Surface-emitting laser diode having reduced device resistance and capable of performing high output operation, surface-emitting laser diode array, electrophotographic system, surface-emitting laser diode module, optical telecommunication system, optical interconnection system using the surface-emitting laser diode, and method of fabricating the surface-emitting laser diode

ABSTRACT

A surface-emitting laser diode device that oscillates in a direction perpendicular to the substrate is provided. This surface-emitting laser diode device includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element. In this surface-emitting laser diode, the area of the non-oxide region is smaller than the area of the hole restricting structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is based on Japanese Laid-Open Patent ApplicationNos. 2002-46373, 2002-373863, 2002-228702, and 2003-32758, filed on Feb.22, 2002, Dec. 25, 2002, Aug. 6, 2002, and Feb. 10, 2003, respectively,the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a surface-emitting laser diode, asurface-emitting laser diode array, an electrophotographic system, asurface-emitting laser diode module, an optical communication system, anoptical interconnection system using the surface-emitting laser diode,and a method of fabricating the surface-emitting laser diode.

A surface-emitting laser (a surface-emitting laser diode) has an activelayer that is smaller in volume than that of an edge-emitting laser, andcan perform high-speed modulation. For this reason, surface-emittinglasers are attracting more attention as light sources for communicationsuch as Gigabit Ethernet (a trademark name). As a surface-emitting lasercan have laser outputs in the direction perpendicular to the substrate,it is easy to form a two-dimensional array with surface-emitting lasers.Also, as such a two-dimensional array consumes less electricity,surface-emitting lasers are also expected to serve as light sources forparallel optical interconnection.

Conventionally, to achieve low threshold current in a surface-emittinglaser, a current restricting structure has been employed. This currentrestricting structure is formed by an oxide of an Al mixed crystal inthe following manner. For example, Non-Patent Document 1 discloses acurrent restricting structure formed by a selective oxidation structurein a device that includes an InGaAs/GaAs quantum well active layerformed through crystal growth by a metal organic chemical vapordeposition (MOCVD) technique, and AlAs/GaAs distributed Bragg reflectorsthat sandwich the quantum well active layer.

In accordance with this conventional technique, after the crystal growthof the device, etching is cylindrically performed on an area of 20 μm indiameter on the surfaces of the device and the substrate. Annealing isthen performed, at 400° C., in a steam atmosphere that is formed byfrothing water, heated at 80° C., with nitrogen gas. By doing so, onlythe AlAs layers that extend from the side of the cylindrical portion tothe center of the mesa are selectively oxidized, so that an AlxOycurrent restricting structure is formed in the region surrounding thecylindrical portion, with a current passage having a diameter of 5 μmbeing maintained at the center of the cylindrical portion. As the AlxOycurrent restricting structure exhibits high insulation, current can beefficiently restricted to the region that has not been oxidized. Withthis structure, the device realizes an extremely low threshold value of70 μA.

Further, the refractive index of AlxOy is approximately 1.6, which islower than the refractive index of the other semiconductor layers.Because of this, a transverse-direction refraction difference is causedin the resonator structure, and oscillating light is confined in thecenter region of the mesa. Accordingly, diffraction loss is reduced, andthe device efficiency is increased. However, the amount of confinedlight increases at the same time. To suppress high-order transverse-modeoscillation, the size of the oxidation confinement structure needs to besmall.

In a structure having an oxidation confinement structure formed throughselective oxidation performed on the low refraction layer of thedistributed Bragg reflectors, the amount of confined light becomesextremely large, as the oxidation confinement structure occupies most ofthe area of the distributed Bragg reflectors. It is therefore necessaryto form a very small oxidation confinement structure, so as to suppresshigh-order transverse-mode oscillation. However, a very small oxidationconfinement structure causes various problems, such as an increase ofresistance, as will be described later in detail. For this reason, thelow refraction layers of the distributed Bragg reflectors are notoxidized in a conventional surface-emitting laser diode device thatemploys an oxidation confinement structure. Instead, a singleselectively oxidized layer for oxidation confinement is provided in ap-type distributed Bragg reflector, in addition to the low refractionlayers of the distributed Bragg reflectors, so that the amount of lightconfined in the transverse direction is reduced, and that the oxidationconfinement structure for suppressing high-order transverse-modeoscillation has a size large enough for practical use. This structurefor confining current and confining light in is commonly employed inconventional devices.

A conventional surface-emitting laser diode device that employs a singleoxidation confinement structure can achieve single fundamental modeoscillation, with the diameter of the oxidation confinement structurebeing limited to three to four times as long as the oscillationwavelength, which might vary with wavelength band that is being usedthough. In this manner, decreases of the oscillation threshold anddiffraction loss and single fundamental mode control are realized withan oxidation confinement structure.

As a conventional technique of performing single fundamentaltransverse-mode control with an oxidation structure with higherefficiency, Non-Patent Document 2 discloses transverse-mode controlusing an MOX (multiple oxide) structure. In accordance with thisconventional technique, a p-type distributed Bragg reflector includes anoxidation structure for confining current (confining holes) and an MOXstructure that is formed on the oxidation structure and has two or moreoxidation structures having larger oxidation sizes. Here, the two ormore oxidation structures having larger oxidation sizes are employedmainly to reduce the parasitic capacitance of the device, but also havean effect of suppressing high-order transverse-mode oscillation.

While the fundamental transverse mode exhibits great electric fieldamplitude at the center of the mesa, the high-order transverse modenormally exhibits great electric field amplitude in a peripheral regionat a distance from the center of the mesa. If a low refraction structureis formed through oxidation in the region surrounding the mesa in thisstructure, high-order transverse-mode diffraction (leakage) loss iscaused, and, as a result, oscillation is suppressed. Since thefundamental transverse mode exhibits great electric field amplitude atthe center of the mesa that is not oxidized, the diffraction loss due toan oxidation structure having a large size is small with the fundamentaltransverse mode. Accordingly, the oscillation mode can be moreefficiently switched to the fundamental transverse mode. In thisexample, a three-layer oxidation structure is employed, separately froma current restricting structure, to perform single fundamentaltransverse-mode control with high efficiency.

[Non-Patent Document 1]

-   -   Electronics Letters 31 (1995), pp. 560-562

[Non-Patent Document 2]

-   -   Collection of Preliminary Lecture Manuscripts for the 47th        Associated Lecture Meeting on Applied Physics, p. 29, N-2.

As described above, to achieve single transverse-mode oscillation with acurrent restricting structure, the size of the oxidation structure needsto be small, and the loss with the high-order mode needs to beincreased. By reducing the size of the oxidation confinement structure,the threshold current can be lowered, but the area that contributes tooscillation is reduced. As a result, it becomes difficult to achievehigh outputs.

In addition to the above problem, the device resistance increases withthe decrease of the area of the conductive region, and high-outputoscillation becomes difficult due to output saturation caused by deviceheat generation. Especially with a p-type semiconductor material, theeffective mass of holes is great, and the mobility is low. Even if abuffer layer such as a heterospike buffer layer is inserted in theinterface, the resistance of the distributed Bragg reflector is high.Because of these factors, the device resistance greatly increases with adecrease of the size of the oxidation confinement structure.

On the other hand, if a large oxidation confinement structure is formed,the oscillation region becomes broader, and accordingly, relatively highoutputs can be obtained. However, such a large oxidation confinementstructure cannot effectively suppress high-order transverse-modeoscillation, resulting in frequent occurrence of high-ordertransverse-mode oscillation.

For the above reasons, single fundamental transverse-mode oscillationcannot be achieved with high outputs. Conventionally, to achieve singlefundamental transverse-mode oscillation with a single oxidationconfinement structure, each side or the diameter of the oxidationconfinement structure needs to be three to four times as long as theoscillation wavelength, which might vary with the wavelength band thatis being used. Even with the oxidation confinement structure of such asize, the highest possible output that can be expected is only 2 mW orso.

In many cases where a surface-emitting laser is employed as a lightsource or a WRITE light source, such as in an electrophotographicsystem, an optical disk write system, and a long-distance communicationusing optical fibers, it is strongly desired to obtain single-peakedbeams or single fundamental transverse-mode oscillation. In view ofthis, single fundamental transverse-mode control with a selectiveoxidation structure having a very small non-oxide region is essentialfor a surface-emitting laser diode.

As described so far, a conventional surface-emitting laser diode of anoxidation confining type simultaneously performs current restricting andsingle fundamental transverse-mode control with one selective oxidationstructure having a very small non-oxide region. Although such asurface-emitting laser diode can achieve very low threshold current andsignal fundamental transverse-mode oscillation, the device resistance isvery high. Furthermore, it is difficult to have high outputs, because ofthe smaller oscillation region and an increase of heat generation due tothe higher resistance. As the device resistance is very high, it is alsodifficult to perform high-speed modulation.

In the structure disclosed in the Non-Patent Document 1, which employsan oxidation confinement structure formed through selective oxidationperformed on the low refraction layers of the distributed Braggreflectors, the amount of confinement is too large, and the size of theoxidation confinement structure needs to be reduced to suppresshigh-order transverse-mode oscillation. Further, as the oxidationconfinement structure that confines holes occupies most of the area ofthe p-type distributed Bragg reflector, the device resistance becomesvery high, and it is very difficult to perform high-output operations.

With the MOX structure disclosed in Non-Patent Document 2, on the otherhand, high-order transverse-mode oscillation can be suppressed, and theparasitic capacitance can be reduced. However, since a number ofoxidation confinement structures are provided in one p-type Braggreflector, the device resistance becomes very high. Also, as anoxidation confinement structure of a small size is employed as the holerestricting structure, the device resistance is still very high, and itis difficult to have high outputs.

SUMMARY OF THE INVENTION

Therefore, it is a general object of the present invention to provide asurface-emitting laser diode, a surface-emitting laser diode array thatincludes the surface-emitting laser diode, an electrophotographicsystem, a surface-emitting laser diode module, an optical communicationsystem, an optical interconnection system, and a method of fabricatingthe surface-emitting laser diode in which the above disadvantages areeliminated.

A more specific object of the present invention is to provide asurface-emitting laser diode that has a low device resistance and canperform high-output operations while maintaining single fundamentaltransverse-mode oscillation with high outputs, a surface-emitting laserdiode array that includes the surface-emitting laser diode, anelectrophotographic system, a surface-emitting laser diode module, anoptical communication system, an optical interconnection system, and amethod of fabricating the surface-emitting laser diode.

The above objects of the present invention are achieved by asurface-emitting laser diode device that includes: an active layer; aresonator structure that includes a first distributed Bragg reflectorand a second distributed Bragg reflector that face each other andsandwich the active layer; a hole passage that extends from a firstelectrode to the active layer; an electron passage that extends from asecond electrode to the active layer; a hole restricting structure thatis located in the hole passage and defines a region for confining holesto the active layer; and an optical mode control structure that includesa non-oxide region formed in the resonator structure, and an oxideregion surrounding the non-oxide region, each region containing Al as aconstituent element. In this optical mode control structure, the area ofthe non-oxide region is smaller than the area of the hole restrictingstructure. Accordingly, this surface-emitting laser diode device has alow device resistance, and can perform high-output operations, whilemaintaining single fundamental transverse-mode oscillation. Here, thehole restricting structure typically includes a non-oxide region and anoxide region surrounding the non-oxide region, and each of the regionscontains Al as a constituent element. The oxide region and the non-oxideregion of each of the hole restricting structure and the optical modecontrol structure are typically formed by performing selective oxidationon a part of a semiconductor layer that contains Al as a constituentelement.

In this surface-emitting laser diode device, each structure that includethe oxide region and the non-oxide region formed through selectiveoxidation performed on a semiconductor layer containing Al as aconstituent element is referred to as a selective oxidation structure.Each semiconductor layer that forms such a selective oxidation structurethrough partial selective oxidation is referred to as a selectivelyoxidized layer.

Conventionally, a surface-emitting laser diode device has a structure inwhich one oxidation structure performs both single fundamentaltransverse-mode control and current restricting. Such an oxidationstructure is provided on the hole confining side having a higher carrierrestricting efficiency. Between the two types of carriers, holes havelower mobility than electrons. After restriction, holes rarely scatter,and can maintain great confining effects. Also, the diameter or eachside of the non-oxide region of the hole restricting structure is onlythree to five times as long as the oscillation wavelength, so as tosuppress high-order transverse-mode oscillation and to achieve singlefundamental transverse-mode oscillation. However, as the mobility ofholes is low, the confining part of the hole restricting structure islikely to have high resistance. Even if the area of the non-oxide(conductive) region is reduced so as to achieve single fundamentaltransverse-mode oscillation, the device resistance becomes very high.

In accordance with the present invention, on the other hand, twoselective oxidation structures including non-oxide (conductive) regionshaving different areas from each other are respectively provided in thep-type and n-type semiconductor layers that are located in the hole andelectron passages. Furthermore, the area of the non-oxide (conductive)region that is located in the electron passage is smaller than the areaof the non-oxide (conductive) region that is located in the holepassage.

The selective oxidation structure having the smaller non-oxide region inthe electron passage functions as an optical mode control structure tosuppress high-order transverse-mode oscillation, while the selectiveoxidation structure having the larger non-oxide region in the holepassage functions as a hole restricting structure. In this manner, ahole restricting structure and an optical mode control structure areprovided separately from each other, and the optical mode controlstructure that requires a very small non-oxide region is provided in theelectron passage (in an n-type semiconductor) that does not increaseresistance. Thus, increases of device resistance are prevented.

To achieve the same objective as the above, the present invention alsoprovides a structure in which two selective oxidation structuresincluding non-oxide regions having different areas from each other arerespectively provided in the hole passage (in a p-type semiconductor)and in a region that does not meet the carrier passages (the electronpassage and the hole passage). In this structure, the area of thenon-oxide region located outside the carrier passages is smaller thanthe area of the non-oxide region located in the hole passage.

Here, the selective oxidation structure including the smaller non-oxideregion located outside the carrier passages serves as an optical modecontrol structure, while the selective oxidation structure having thelarger non-oxide region located in the hole passage serves as a holerestricting structure. In this manner, the hole restricting structureand the optical mode control structure are provided separately from eachother, and the optical mode control structure requiring a very smallnon-oxide region is located in a region that does not meet the carrierpassages and does not affect the device resistance. Thus, increases ofdevice resistance can be prevented.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the structure of a surface-emitting laser diode ofExample 1 of the present invention;

FIG. 2 illustrates the resonance region (the region of the resonator) ofthe surface-emitting laser diode of FIG. 1, in conjunction with thestanding wave of oscillating light;

FIG. 3 illustrates the structure of a surface-emitting laser diode ofExample 2 of the present invention;

FIG. 4 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 3, in conjunction of the standingwave of oscillating light;

FIG. 5 illustrates the structure of a surface-emitting laser diode ofExample 3 of the present invention;

FIG. 6 illustrates the resonance region of the surface-emitting laserdiode of FIG. 5, and the region in which a p-AlAs selectively oxidizedlayer is provided in a p-Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector;

FIG. 7 illustrates the structure of a surface-emitting laser diode ofExample 4 of the present invention;

FIG. 8 illustrates the surface-emitting laser diode of FIG. 7 in greaterdetail;

FIG. 9 illustrates the structure of a surface-emitting laser diode ofExample 5 of the present invention;

FIG. 10 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 9;

FIG. 11 illustrates the structure of a surface-emitting laser diode ofExample 6 of the present invention;

FIG. 12 illustrates the surrounding area of the resonance region of theintra-cavity contact type surface-emitting laser diode of FIG. 11;

FIG. 13 illustrates the structure of a surface-emitting laser diode ofExample 7 of the present invention;

FIG. 14 illustrates the resonance region of the surface-emitting laserdiode of FIG. 13 in greater detail;

FIG. 15 illustrates the structure of a surface-emitting laser diode ofExample 8 of the present invention;

FIG. 16 illustrates the surrounding area of the resonance region of theintra-cavity contact type surface-emitting laser diode of FIG. 15;

FIG. 17 illustrates the structure of a surface-emitting laser diode ofExample 9 of the present invention;

FIG. 18 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 17;

FIG. 19 illustrates the structure of a surface-emitting laser diode ofExample 10 of the present invention;

FIG. 20 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 19;

FIG. 21 illustrates the structure of a surface-emitting laser diode ofExample 11 of the present invention;

FIG. 22 illustrates the resonance region of the surface-emitting laserdiode of FIG. 21 in greater detail;

FIG. 23 illustrates the structure of a surface-emitting laser diode ofExample 12 of the present invention;

FIG. 24 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 23;

FIG. 25 illustrates the structure of a surface-emitting laser diode ofExample 13 of the present invention;

FIG. 26 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 25;

FIG. 27 illustrates the structure of a surface-emitting laser diode ofExample 14 of the present invention;

FIG. 28 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 27, in conjunction with thestanding wave of oscillating light;

FIG. 29 illustrates the structure of a surface-emitting laser diode ofExample 15 of the present invention;

FIG. 30 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 29, in conjunction with thestanding wave of oscillating light;

FIG. 31 illustrates the structure of a surface-emitting laser diode ofExample 16 of the present invention;

FIG. 32 illustrates the structure of a surface-emitting laser diode ofExample 17 of the present invention;

FIG. 33 illustrates the structure of a surface-emitting laser diode ofExample 18 of the present invention;

FIG. 34 illustrates the surrounding area of the resonance region of thesurface-emitting laser diode of FIG. 33 in greater detail;

FIG. 35 illustrates the structure of a surface-emitting laser diodearray of Example 19 of the present invention;

FIG. 36 illustrates the structure of a multi-wave surface-emitting laserdiode array of Example 20 of the present invention;

FIG. 37 also illustrates the structure of the multi-wavesurface-emitting laser diode array of Example 20 of the presentinvention;

FIG. 38 illustrates the structure of a surface-emitting laser diode ofExample 21 of the present invention;

FIG. 39 illustrates the structure of a surface-emitting laser diode ofExample 22 of the present invention;

FIG. 40 illustrates the structure of an electrophotographic system ofExample 23 of the present invention;

FIG. 41 schematically illustrates a surface-emitting laser diode moduleof Example 24 of the present invention;

FIG. 42 illustrates the structure of an optical interconnection systemof Example 25 of the present invention;

FIG. 43 illustrates the structure of an optical communication system ofExample 26 of the present invention; and

FIG. 44 illustrates the structure of a wavelength division multiplexing(WDM) communication system of Example 27 of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Principles of the Present Invention)

The following is the summary of the structures and the functions/effectsof the present invention.

The first advantageous feature of the present invention is to provide asurface-emitting laser diode device that oscillates in a directionperpendicular to a substrate. This surface-emitting laser diode deviceincludes: an active layer; a resonator structure including a firstdistributed Bragg reflector and a second distributed Bragg reflectorthat face each other and sandwich the active layer; a hole passage thatextends from a first electrode to the active layer; an electron passagethat extends from a second electrode to the active layer; a holerestricting structure that is located in the hole passage and defines aregion for confining holes to the active layer; and an optical modecontrol structure that includes a non-oxide region provided in theresonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element. In thissurface-emitting laser diode device, the area of the non-oxide region issmaller than the area of the hole restricting structure.

Also, in this surface-emitting laser diode device, the hole restrictingstructure includes a non-oxide region and an oxide region surroundingthe non-oxide region, both regions being formed out of a semiconductorlayer containing Al as a constituent element.

Further, in this surface-emitting laser diode device, the holerestricting structure and the optical mode control structure eachincludes an oxide region and a non-oxide region that are formed throughselective oxidation performed on a part of a semiconductor layer, eachregion containing Al as a constituent element.

Also, in this surface-emitting laser diode device, to prevent increasesof the device resistance, a selective oxidation structure (an opticalmode control structure) to suppress high-order transverse-modeoscillation is provided separately from the hole restricting structure,and the area of the non-oxide region in the optical mode controlstructure is smaller than the area of the non-oxide region in the holerestricting structure.

With this structure in which the hole restricting structure and theoptical mode control structure are employed separately, it is possibleto design each layer optimally and independently. Here, the optical modecontrol structure is located in such a position that adverse influenceon the device resistance can be minimized even if the non-oxide regionis very small. In this manner, increases of the device resistance can beprevented.

As the separately provided optical mode control structure suppresseshigh-order transverse-mode oscillation, the hole restricting structuredoes not need to suppress the high-order transverse-mode oscillation.Accordingly, the area of the non-oxide region of the hole restrictingstructure does not need to be so small as to increase the resistance.Thus, a low-resistance device can be obtained. Even if the non-oxideregion of the hole restricting structure has a large area, holes canconcentrate at the center of the mesa in the active layer region, asholes have great confinement effects. Accordingly, it is possible toprevent non-emitting re-coupling on the side surfaces of the mesa, andto maintain high internal quantum efficiency. Also, the oscillationregion can be enlarged, and the outputs can be increased, by increasingthe area of the non-oxide region of the hole restricting structure.Further, as heat generation is reduced with the lower resistance,high-output operations can be performed. As the resistance becomeslower, it is also possible to perform high-speed modulation.

The second advantageous feature of the present invention is to provide asurface-emitting laser diode device in which the optical mode controlstructure is located in the electron passage in the surface-emittinglaser diode device.

As described above, holes have lower mobility and greater restrictioneffects than electrons. However, holes often increase the resistance dueto the low mobility and restriction. On the other hand, electrons easilyscatter after restriction, and therefore, are not suitable forrestriction, though electrons do not increase the device resistancealong with the restriction.

Therefore, in the surface-emitting laser diode device having the secondadvantageous feature of the present invention, the optical mode controlstructure that is provided separately from the hole restrictingstructure and has a small non-oxide region is located in the electronpassage, so as to prevent increases of resistance.

As the optical mode control structure having a small non-oxide region islocated in the electron passage, a rapid increase of the deviceresistance can be prevented, and high-order transverse-mode oscillationcan be effectively suppressed.

The third advantageous feature of the present invention is to provide asurface-emitting laser diode device in which the optical mode controlstructure is provided in a region that does not meet the electronpassage and the hole passage in the surface-emitting laser diode device.

In this surface-emitting laser diode device having the thirdadvantageous feature of the present invention, the optical mode controlstructure that is formed by a selective oxidation structure having asmaller non-oxide region is located in a region that does not meet thecarrier passages (the electron passage and the hole passage).

As the optical mode control structure is located in a region that doesnot meet the carrier passages, the device resistance does not depend onthe area of the non-oxide region of the optical mode control structure.Also, as the optical mode control structure is provided separately fromthe hole restricting structure, the area of the non-oxide layer of thehole restricting structure does not need to be small. With a non-oxideregion that has a larger area than a conventional non-oxide region,increases of the device resistance can be prevented.

In a case where the optical mode control structure is provided in acarrier passage, the device resistance automatically increases with adecrease of the area of the non-oxide region. However, the optical modecontrol structure that is located outside the carrier passages does notaffect the device resistance. Therefore, this structure is suitableespecially for a short-wavelength surface-emitting laser to which a verysmall non-oxide region is essential.

The fourth advantageous feature of the present invention is to provide asurface-emitting laser diode device in which the part of the holerestricting structure that defines the region for confining holes isformed by a p-type semiconductor layer.

In this surface-emitting laser diode device having the fourthadvantageous feature of the present invention, the semiconductor layerthat is provided in the hole passage and contains Al as a constituentelement is a p-type layer. As already mentioned, the resistance in thesurface-emitting laser diode having an oxidation confinement structureis mostly the resistance of the non-oxide conductive regions that arethe carrier confining parts. To reduce the device resistance, it isessential to reduce the resistance of the non-oxide regions.

The location of the selectively oxidized layer in the hole passage canbe in a semiconductor distributed Bragg reflector or a resonator spacerlayer. However, a resonance region (or a resonator spacer layer) isnormally a non-doped region (layer). If a non-doped selectively oxidizedlayer is provided in such a resonance region, the resistance becomesvery high due to oxidation confinement. Therefore, a p-type layer isused as a selectively oxidized layer that forms the hole restrictingstructure in the hole passage. With this structure, the resistance canbe effectively reduced. Thus, a surface-emitting laser diode with lowresistance can be obtained.

The fifth advantageous feature of the present invention is to provide asurface-emitting laser diode device in which the part of the holerestricting structure that defines the region for confining holes isformed by a p-type semiconductor layer, while the non-oxide region inthe optical mode control structure is formed by an n-type semiconductorlayer.

In this surface-emitting laser diode device having the fifthadvantageous feature of the present invention, the semiconductor layerthat is provided in the hole passage and contains Al as a constituentelement is a p-type layer, and the semiconductor layer that is providedin the electron passage and contains Al as a constituent element is ann-type layer. As already mentioned, the resistance in thesurface-emitting laser diode having an oxidation confinement structureis mostly the resistance of the non-oxide conductive regions that arethe carrier confining parts. To reduce the device resistance, it isessential to reduce the resistance of the non-oxide regions.

The selectively oxide layers in the electron and hole passages can be ina semiconductor distributed Bragg reflector or a resonator spacer layer.However, a resonance region (or a resonator spacer layer) is normally anon-doped region (layer). If a non-doped selectively oxidized layer isprovided in such a resonance region, the resistance becomes very highdue to oxidation confinement. Therefore, a p-type layer is used as aselectively oxidized layer that forms the hole restricting structure inthe hole passage, and an n-type layer is used as a selectively oxidizedlayer that forms the optical mode control structure in the electronpassage. With this structure, the resistance of the respective carrierscan be effectively reduced. Thus, a surface-emitting laser diode withlow resistance can be obtained.

The sixth advantageous feature of the present invention is to provide asurface-emitting laser diode device in which the first distributed Braggreflector and the second distributed Bragg reflector are formed bylaminated structures of semiconductor layers.

In this surface-emitting laser diode device having the sixthadvantageous feature of the present invention, distributed Braggreflectors that are made of semiconductor materials are employed. Withthe distributed Bragg reflectors made of semiconductor materials, allthe layers that constitute the device can be formed by a one-timecrystal growth process. Also, the layers that require high thicknessprecision, such as the resonance region and the distributed Braggreflectors, can be formed with high controllability by the same singleapparatus.

Furthermore, it is possible to employ a semiconductor processingtechnique with high controllability. Thus, highly reliable devices withuniform characteristics can be obtained.

The seventh advantageous feature of the present invention is to providea surface-emitting laser diode device in which one of the firstdistributed Bragg reflector and the second distributed Bragg reflectoris formed by a laminated structure of semiconductor layers, while theother one is formed by a laminated structure of semiconductor ordielectric layers.

In this surface-emitting laser diode device having the seventhadvantageous feature of the present invention, the distributed Braggreflectors are made of semiconductor and dielectric materials. Adielectric material generally has a lower light absorptivity than asemiconductor material, and a high reflection rate can be obtained witha small number of dielectric layers. Absorption loss causes problemssuch as increases of the oscillation threshold current and decreases ofthe slope efficiency and output. As the doping concentration increasesin a semiconductor material, absorptivity among free carriers andvalence electrons becomes higher, resulting in an increase of lightabsorption loss. Also, light absorptivity becomes higher with a longerwavelength. Because of these facts, it is difficult to obtain along-wave device with excellent characteristics. On the other hand, witha distributed Bragg reflector made of a dielectric material, theabsorption loss of oscillating light can be reduced, and a device withexcellent characteristics can be obtained. More specifically, asurface-emitting laser diode that exhibits excellent characteristicsespecially in long wavelength bands can be obtained. Accordingly, asurface-emitting laser diode of the present invention has low resistanceand can achieve fundamental single transverse-mode oscillation with highoutputs. As the resistance is low, it is also possible to performhigh-speed modulation. Especially with the seventh advantageous featureof the present invention, a surface-emitting laser diode that issuitable for optical fiber communication can be provided. In short, withthe seventh advantageous feature of the present invention, asurface-emitting laser diode device that has low device resistance, lowabsorptivity, and high operation efficiency, is provided. Thissurface-emitting laser diode device can perform high-output operations,and achieve fundamental single transverse-mode oscillation even withhigh outputs.

Here, the distributed Bragg reflector that is formed by dielectric andsemiconductor materials may have the low refraction layer and the highrefraction layer made of dielectric materials, or dielectric andsemiconductor materials. Also, one of the distributed Bragg reflectorsthat sandwich the active layer may be made only of semiconductormaterials.

The eighth advantageous feature of the present invention is to provide asurface-emitting laser diode device in which at least one of the firstdistributed Bragg reflector and the second distributed Bragg reflectoris a semiconductor Bragg reflector having a laminated structure ofn-type semiconductor layers, and that a tunnel junction is interposedbetween the n-type semiconductor Bragg reflector and the active layer.

In this surface-emitting laser diode device having the eighthadvantageous feature of the present invention, at least one of thedistributed Bragg reflectors is an n-type semiconductor Bragg reflector,and a tunnel junction is provided between the n-type semiconductor Braggreflector and the active layer. As already mentioned, a semiconductorBragg reflector tends to have greater absorption loss with doping, andthis tendency is greater with a p-type semiconductor Bragg reflector. Onthe other hand, with low-concentration doping, there is the problem ofhigher device resistance. Therefore, with a p-type semiconductor Braggreflector, it is difficult to obtain a device that excels in bothoptical characteristics (low absorptivity) and electric characteristics.However, a tunnel junction can generate and guide holes into the activeregion through the p-n junction of thin films that are doped with highconcentration and are counter-biased through the tunneling betweenbands. Accordingly, with a tunnel junction, it is possible to guideelectrons and holes into the active region, without a p-typesemiconductor Bragg reflector.

With the eighth advantageous feature of the present invention, it ispossible to reduce the absorption loss due to the semiconductor Braggreflectors, and thereby to obtain a surface-emitting laser diode thathas low oscillation threshold current, high slope efficiency, and highoutputs. Accordingly, the surface-emitting laser diode device having theeighth advantageous feature of the present invention has low resistance,and can achieve fundamental single transverse-mode oscillation with highoutputs. As the device resistance is low, it is also possible to performhigh-speed modulation. Furthermore, with the eighth advantageous featureof the present invention, it is possible to obtain a surface-emittinglaser diode that exhibits excellent characteristics in long wavelengthbands in which light absorptivity by semiconductors becomes higher.Accordingly, a surface-emitting laser diode that is suitable especiallyfor communication can be obtained. In short, with the eighthadvantageous feature of the present invention, a surface-emitting laserdiode device that has low device resistance, low absorptivity, and highoperation efficiency, is provided. This surface-emitting laser diode canperform high-output operations, and achieve fundamental singletransverse-mode oscillation even with high outputs.

The ninth advantageous feature of the present invention is to provide asurface-emitting laser diode device in which at least one of the firstdistributed Bragg reflector and the second distributed Bragg reflectorincludes a laminated structure of non-doped semiconductor layers, andone of the first electrode and the second electrode is provided on asemiconductor layer interposed between the active layer and thedistributed Bragg reflector that includes the laminated structure of thenon-doped semiconductor layer.

In this surface-emitting laser diode device having the ninthadvantageous feature of the present invention, at least one of thedistributed Bragg reflectors is a non-doped semiconductor Braggreflector or a Bragg reflector that includes a region that is partiallyformed by a non-doped semiconductor Bragg reflector. Furthermore, anelectrode for confining carriers is provided on a semiconductor layerbetween the active layer and the non-doped semiconductor Bragg reflectoror the region that is partially formed by a non-doped semiconductorBragg reflector.

As already mentioned, a semiconductor Bragg reflector tends to havehigher light absorptivity with higher-concentration doping. Because ofthis tendency, a surface-emitting laser diode that employs a p-typesemiconductor distributed Bragg reflector does not excel in both opticalcharacteristics (low absorptivity) and electric characteristics.However, a partially non-doped or totally non-doped semiconductordistributed Bragg reflector can be employed in a surface-emitting laserdiode of an intra-cavity contact type that has an electrode forconfining carriers on a semiconductor layer in the device. With thisstructure, light absorption by the distributed Bragg reflector in thenon-doped region can be reduced.

In an n-type semiconductor, free carrier absorptivity also increases,though slightly, with high-concentration doping, resulting in higherlight absorptivity. With a partially or totally non-doped distributedBragg reflector, regardless of the conductivity type, the absorptionloss of oscillation light can be reduced. It is thus possible to obtaina device that has low oscillation threshold current, high slopeefficiency, and high outputs. In this manner, the surface-emitting laserdiode of the present invention has low resistance, and can achievefundamental single transverse-mode oscillation even with high outputs.As the device resistance is low, it is also possible to performhigh-speed modulation. Furthermore, with the ninth advantageous featureof the present invention, it is possible to obtain a surface-emittinglaser diode that exhibits excellent characteristics in long wavelengthbands in which the light absorption by semiconductors becomes greater.Therefore, a surface-emitting laser diode that is suitable especiallyfor communication can be obtained. In short, with the ninth advantageousfeature of the present invention, a surface-emitting laser diode devicethat has low device resistance, low absorptivity, and high operationefficiency, can be provided. This surface-emitting laser diode canperform high-output operations, and achieve fundamental singletransverse-mode oscillation even with high outputs.

The tenth advantageous feature of the present invention is to provide asurface-emitting laser diode device in which the hole restrictingstructure is provided at a location corresponding to an antinode of thestanding wave of oscillating light in the resonator structure.

In this surface-emitting laser diode device having the tenthadvantageous feature of the present invention, the selective oxidationstructure (the hole restricting structure) including an oxide insulatingregion and a non-oxide conductive region formed through selectiveoxidation performed on a selectively oxidized semiconductor layer thatis provided in the hole passage and contains Al as a constituent elementis provided at a location corresponding to an antinode of the standingwave of oscillating light.

Conventionally, the size of the oxidation confinement structure is sosmall as to suppress high-order transverse-mode light that has highelectric field intensity in the region surrounding the mesa. However,this also causes loss in the fundamental transverse-mode light. In aconventional device that reduces the threshold and suppresses thehigh-order transverse-mode light with a single oxidation confinementstructure, an oxidation confinement structure is normally provided at alocation corresponding to a joint of the standing wave that has lowelectric field intensity, so as to maintain the diffraction loss ofoscillating light at a low level.

In a device of the present invention, on the other hand, the suppressingof the high-order transverse-mode light is performed mainly by anoxidation confinement structure located in the electron passage.Therefore, the oxidation confinement structure located in the holepassage should be only as large as to restrict the hole confinementregion to the center of the mesa without a rapid increase of the deviceresistance. Accordingly, it is possible to have a larger area forconfinement than a conventional one, and to reduce loss in thefundamental transverse-mode light. Further, with the oxidationconfinement structure provided at a location corresponding to anantinode of the standing wave, the high-order transverse-mode light thathas high electric field intensity in the region surrounding the mesa canbe suppressed. Thus, high-order mode oscillation can be effectivelysuppressed. In this manner, a surface-emitting laser diode that has lowdevice resistance and can achieve single transverse-mode oscillationwith high outputs can be obtained. In short, with the tenth advantageousfeature of the present invention, it is possible to provide asurface-emitting laser diode that has low device resistance, and canperform high-output operations and achieve single fundamentaltransverse-mode oscillation even with higher outputs.

The eleventh advantageous feature of the present invention is to providea surface-emitting laser diode device in which two or more optical modecontrol structures are provided in the electron passage.

The eleventh advantageous feature of the present invention is also toprovide a surface-emitting laser diode device in which two or moreoptical mode control structures are provided in a region that does notmeet the electron passage and the hole passage.

In this surface-emitting laser diode device having the eleventhadvantageous feature of the present invention, two or more selectiveoxidation structures (optical mode control structures) having relativelysmall non-oxide regions are provided in the electron passage or in aregion that does not meet the electron passage and the hole passage.With the two or more oxide layers, the effect of suppressing high-ordertransverse-mode oscillation can be made greater. If a multi-layerstructure is employed as a selective oxidation structure having a smallnon-oxide region in a conventional device, the device resistanceincreases rapidly. In the present invention, however, a multi-layerstructure does not increase the resistance, because the optical modecontrol structures are provided in the electron passage (an n-typesemiconductor layer) having low electric resistance. Accordingly, singlefundamental transverse-mode selectivity can be increased, without arapid increase of the resistance. In short, with the eleventhadvantageous feature of the present invention, it is possible to providea surface-emitting laser diode device that has low device resistance,and can perform high-output operations and achieve single fundamentaltransverse-mode oscillation even with higher outputs.

The twelfth advantageous feature of the present invention is to providea surface-emitting laser diode device in which the semiconductor layerthat forms the optical mode control structure through selectiveoxidation and contains Al as a constituent element is thicker than thesemiconductor layer that forms the hole restricting structure throughselective oxidation and contains Al as a constituent element.

In this surface-emitting laser diode device having the twelfthadvantageous feature of the present invention, the selectively oxidizedlayer formed by the semiconductor layer that forms the smaller non-oxideregion through selective oxidation and contains Al as a constituentelement is thicker than the selectively oxidized layer formed by thesemiconductor layer that forms the larger non-oxide region throughselective oxidation and contains Al as a constituent element.

A semiconductor mixed crystal such as an AlGaAs mixed crystal containingAl in its composition can be oxidized in a heated steam atmosphere. Indoing so, the oxidation speed depends on the Al composition and thethickness of the semiconductor layer containing Al in its composition.Oxidation progresses more rapidly, if the semiconductor layer has agreater Al content and a greater thickness. Between two semiconductorlayers having the same compositions, it is possible to control the sizesof the oxidation confinement structures by adjusting the thicknesses ofthe selectively oxidized layers to be grown. In this manner, oxidationconfinement structures having different sizes can be obtained through aone-time oxidation process. As the thicknesses of the semiconductorlayers containing Al in the compositions are adjusted in this manner, asurface-emitting laser diode that has low device resistance and canachieve single transverse-mode oscillation with high outputs can beeasily obtained. In short, with the twelfth advantageous feature of thepresent invention, a surface-emitting laser diode that has low deviceresistance, and can perform high-output operations and achieve singlefundamental transverse-mode oscillation with high outputs, can be easilyobtained with high controllability.

The thirteenth advantageous feature of the present invention is toprovide a surface-emitting laser diode device in which the Al content ofthe semiconductor layer that forms the optical mode control structurethrough selective oxidation and contains Al as a constituent element isgreater than the Al content of the semiconductor layer that forms thehole restricting structure through selective oxidation and contains Alas a constituent element.

In this surface-emitting laser diode device having the thirteenthadvantageous feature of the present invention, the Al content of theselectively oxidized layer formed by the semiconductor layer that formsthe smaller non-oxide region through selective oxidation and contains Alin its composition is greater than the Al content of the selectivelyoxidized layer formed by the semiconductor layer that forms the largernon-oxide region through selective oxidation and contains Al in itscomposition.

A semiconductor mixed crystal such as an AlGaAs mixed crystal containingAl in its composition can be oxidized in a heated steam atmosphere. Indoing so, the oxidation speed depends on the Al composition and thethickness of the semiconductor layer containing Al in its composition.Oxidation progresses more rapidly, if the semiconductor layer has agreater Al content and a greater thickness. In a case of an AlGaAs mixedcrystal, oxidation can progress with an Al content ratio of 0.9 or so.

Accordingly, it is possible to control the sizes of the oxidationconfinement structures by adjusting the Al content ratios. In thismanner, oxidation confinement structures having different sizes can beobtained in one device through a one-time oxidation process. As the Alcontents of the semiconductor layers containing Al as a constituentelement are adjusted in this manner, a surface-emitting laser diode thathas low device resistance and can achieve single transverse-modeoscillation with high outputs can be easily obtained. In short, with thethirteenth advantageous feature of the present invention, asurface-emitting laser diode that has low device resistance, and canperform high-output operations and achieve single fundamentaltransverse-mode oscillation with high outputs, can be easily obtainedwith high controllability.

The fourteenth advantageous feature of the present invention is toprovide a surface-emitting laser diode device in which the active layeris formed by a III-V semiconductor material that includes at least oneIII-group element selected from the group of Al, Ga, and In, and atleast one V-group element selected from the group of As and P. Here, theactive layer has an oscillation wavelength shorter than 1.1 μm.

In this surface-emitting laser diode device having the fourteenthadvantageous feature of the present invention, the III-V semiconductormaterial that forms the active layer contains at least one III-groupelement selected from the group of Al, Ga, and In, and at least oneV-group element selected from the group of As and P. With thisstructure, the oscillation wavelength becomes shorter than 1.1 μm, andtherefore it is possible to obtain a surface-emitting laser diode thatexhibits low device resistance in short-wave band areas, and can performhigh-output operations and achieve single fundamental transverse-modeoscillation with high outputs. To perform single fundamentaltransverse-mode control in a surface-emitting laser diode having anoscillation wavelength shorter than 1.1 μm, each side of the non-oxideregion needs to be 5 μm or shorter, which results in a rapid increase ofthe device resistance. In accordance with the fourteenth advantageousfeature of the present invention, however, the device resistance can bevery effectively reduced.

This can be achieved with high efficiency especially with a visible-bandsurface-emitting laser. For example, with an AlGaInP-based material usedas the active layer, a red surface-emitting laser diode having anoscillation wavelength band of 660 nm can be obtained. To achieve singlefundamental transverse-mode oscillation in such a surface-emitting laserdiode, each side of the smaller non-oxide region needs to be 3 μm orshorter, which results in a rapid increase of the resistance due toconfinement.

In the device of the present invention, however, the high-ordertransverse-mode suppressing layer that requires a very small non-oxideregion is provided in the electron passage (in an n-type semiconductor)that does not increase the resistance, or in a region that does not meetthe carrier passages and does not affect the resistance. With thisstructure, single fundamental transverse-mode control can be performed,without a rapid increase of the device resistance.

In this manner, a surface-emitting laser diode that has an oscillationwavelength shorter than 1.1 μm can have low device resistance andperform high-output operations, while maintaining single fundamentaltransverse-mode oscillation.

The fifteenth advantageous feature of the present invention is toprovide a surface-emitting laser diode device in which the active layeris formed by a III-V semiconductor material that includes at least oneIII-group element selected from the group of Ga and In, and at least oneV-group element selected from the group of As, P, N, and Sb. Here, theactive layer has an oscillation wavelength longer than 1.1 μm.

In this surface-emitting laser diode device having the fifteenthadvantageous feature of the present invention, the III-V semiconductormaterial that forms the active layer contains at least one III-groupelement selected from the group of Ga and In, and at least one V-groupelement selected from the group of As, P, N, and Sb. With thisstructure, the oscillation wavelength becomes longer than 1.1 μm, andtherefore it is possible to obtain a surface-emitting laser diode thatexhibits low device resistance in long-wave band areas, and can performhigh-output operations and achieve single fundamental transverse-modeoscillation with high outputs. A surface-emitting laser diode having anoscillation wavelength longer than 1.1 μm is essential as a light sourcefor communication using quartz fibers. Particularly, a 1.3 μm band is aband in which quartz fibers are minutely scattered, and therefore,long-distance, high-speed communication can be performed. Also, a 1.5 μmband is essential as a multi-wave communication band area.

As the device of the present invention has low device resistance,high-speed modulation can be performed. The device of the presentinvention is very suitable as a light source used in high-speedmodulation. As the device of the present invention can also have highoutputs while maintaining single fundamental transverse-modeoscillation, long-distance communication can be performed with highefficiency especially in a 1.3 μm band. Thus, a surface-emitting laserdiode that is suitable as a light source for optical communication canbe obtained.

In this manner, with the fifteenth advantageous feature of the presentinvention, a surface-emitting laser diode having an oscillationwavelength of 1.1 μm to 1.6 μm can be obtained on a GaAs substrate. On aGaAs substrate, it is possible to employ a distributed Bragg reflectormade of an AlGaAs mixed crystal with excellent characteristics, and tothereby obtain a device with excellent characteristics. Furthermore, aGaInNAs material in which a very small amount of nitrogen is added toGaInAs by several percents has a great conductive band discontinuitywith respect to a GaAs barrier layer or the like, and exhibits bettertemperature characteristics than a conventional device of the samewavelength band formed on an InP substrate. While a surface-emittinglaser diode device having any of the first through eleventh features ofthe present invention has low device resistance and can achieve singletransverse-mode oscillation with high outputs, a surface-emitting laserdiode device having the fifteenth advantageous feature of the presentinvention can further have a constantly high connecting rate withoptical fibers or the likes. Thus, a surface-emitting laser diode thatis suitable for optical fiber communication can be obtained.

The sixteenth advantageous feature of the present invention is toprovide a surface-emitting laser diode array that is monolithicallyformed on a substrate. Each of the devices that form thissurface-emitting laser diode array includes: an active layer; aresonator structure including a first distributed Bragg reflector and asecond distributed Bragg reflector that face each other and sandwich theactive layer; a hole passage that extends from a first electrode to theactive layer; an electron passage that extends from a second electrodeto the active layer; a hole restricting structure that is located in thehole passage and defines a region for confining holes to the activelayer; and an optical mode control structure that includes a non-oxideregion provided in the resonator structure and an oxide regionsurrounding the non-oxide region, each region containing Al as aconstituent element, and the area of the non-oxide region being smallerthan the area of the hole restricting structure.

In this surface-emitting laser diode array having the sixteenthadvantageous feature of the present invention is formed bysurface-emitting laser diodes having one of the first through fifteenthadvantageous features of the present invention. As a result, asurface-emitting laser diode array that has low device resistance, andcan perform high-output operations and achieve single fundamentaltransverse-mode oscillation with high outputs, can be provided. Inaccordance with the sixteenth advantageous feature of the presentinvention, a monolithic laser diode array is formed by surface-emittinglaser diodes having any of the first through fifteenth advantageousfeatures of the present invention. It is thus possible to provide asurface-emitting laser diode array that has low device resistance andcan achieve fundamental transverse-mode oscillation even with highoutputs. This surface-emitting laser diode array is suitable as a lightsource in a multi-beam write system in an electrophotographic system orin a long-distance optical communication system.

The seventeenth advantageous feature of the present invention is toprovide a surface-emitting laser diode array that is monolithicallyformed on a substrate. Each of the devices that form thissurface-emitting laser diode array includes: an active layer; aresonator structure including a first distributed Bragg reflector and asecond distributed Bragg reflector that face each other and sandwich theactive layer; a hole passage that extends from a first electrode to theactive layer; an electron passage that extends from a second electrodeto the active layer; a hole restricting structure that is located in thehole passage and defines a region for confining holes to the activelayer; and an optical mode control structure that includes a non-oxideregion provided in the resonator structure and an oxide regionsurrounding the non-oxide region, each region containing Al as aconstituent element, and the area of the non-oxide region being smallerthan the area of the hole restricting structure. Here, the areas of thenon-oxide regions of the optical mode control structures are differentfrom one another among the devices that form the surface-emitting laserdiode array. Also, oscillation wavelengths are different from oneanother among the devices.

This surface-emitting laser diode array having the seventeenthadvantageous feature of the present invention is formed bysurface-emitting laser diodes of two or more types among thesurface-emitting laser diodes having the first through fifteenthadvantageous features. These surface-emitting laser diodes havedifferent oscillation wavelengths resulted from the non-oxide regions ofthe optical mode control structures having different areas. It is thuspossible to provide a multi-wave surface-emitting laser diode array thathas low device resistance, can perform high-output operation and achievesingle fundamental mode oscillation with high outputs, and exhibitsuniform device characteristics within the array.

In this multi-wave surface-emitting laser diode array having theseventeenth advantageous feature of the present invention, the in-planeoscillation wavelengths in the array are varied with the areadifferences among the non-oxide regions of the optical mode controlstructures of the surface-emitting laser diodes. In eachsurface-emitting laser diode of the present invention, the holeconfinign structure and the optical mode control structure are providedseparately from each other. Furthermore, the optical mode controlstructure is provided in an n-type semiconductor layer that does notincrease the resistance, or in a region outside the passages of carriers(electrons and holes) that does not affect the electric resistance.Accordingly, a decrease of the area of the non-oxide region in theoptical mode control structure does not increase the resistance as muchas in a conventional device or does not increase the resistance at allin the case of the optical mode control structure being provided in aregion outside the carrier passages.

As the influence of heat generation due to an increase of resistance canbe suppressed, it is possible to have high outputs, while maintainingfundamental transverse-mode oscillation, with a device having an opticalmode control structure including a small non-oxide region. Also, opticaloutputs can be made uniform among devices. Further, the areas of thenon-oxide regions of the hole restricting structures are made uniform,so that the characteristics such as oscillation threshold current andoperation voltage can be made uniform among the devices. In this manner,a multi-wave surface-emitting laser diode array that exhibits uniformcharacteristics and can perform high-output operations can be obtained.

Since the influence of device heat generation (an increase of the deviceresistance) can be reduced, it is possible to produce devices havingvery small non-oxide regions that have conventionally resulted ininsufficient characteristics. It is thus possible to produce deviceshaving shorter oscillation wavelengths. With these devices, a multi-wavesurface-emitting laser diode array that has a broader band area can beobtained.

The eighteenth advantageous feature of the present invention is toprovide a surface-emitting laser diode array in which each of thedevices that form the surface-emitting laser diode array includes two ormore optical mode control structures.

In this multi-wave surface-emitting laser diode array having theeighteenth advantageous feature of the present invention, the number oflayers of optical mode control structures is two or greater in the samestructure as the multi-wave surface-emitting laser diode array havingthe seventeenth advantageous feature of the present invention.

A change of the oscillation wavelength (resonance wavelength) with adecrease of the area of the non-oxide region is caused by a change ofthe transverse-mode extent with an increase of the area of the oxideregion. By reducing the transverse-mode extent, a greater wavelengthchange can be obtained. In accordance with the eighteenth advantageousfeature, two or more optical mode control structures are employed, so asto increase the transverse-mode light confining effect. Thus, amulti-wave surface-emitting laser diode array that has a broader bandarea can be obtained.

Furthermore, in accordance with the eighteenth advantageous feature ofthe present invention, each of the surface-emitting laser diodes thatform the surface-emitting laser diode array having the seventeenthadvantageous feature includes two or more layers of optical mode controlstructures. Accordingly, it is possible to provide a multi-wavesurface-emitting laser diode array that has low device resistance, canperform high-output operations and achieve single fundamental modeoscillation with high outputs, and exhibits uniform devicecharacteristics within the array.

Like the functions and effects in accordance with the seventeenthadvantageous feature of the present invention, it is possible to obtaina multi-wave surface-emitting laser diode array that has low deviceresistance, can perform high-output operations, and exhibits uniformcharacteristics among the surface-emitting laser diodes that form thearray, with the eighteenth advantageous feature of the presentinvention.

The nineteenth advantageous feature of the present invention is toprovide a surface-emitting laser diode module that includes an opticalfiber and a surface-emitting laser diode device that is opticallyconnected to the optical fiber. In this surface-emitting laser diodemodule, the surface-emitting laser diode device includes: an activelayer; a resonator structure including a first distributed Braggreflector and a second distributed Bragg reflector that face each otherand sandwich the active layer; a hole passage that extends from a firstelectrode to the active layer; an electron passage that extends from asecond electrode to the active layer; a hole restricting structure thatis located in the hole passage and defines a region for confining holesto the active layer; and an optical mode control structure that includesa non-oxide region provided in the resonator structure and an oxideregion surrounding the non-oxide region, each region containing Al as aconstituent element, and the area of the non-oxide region being smallerthan the area of the hole restricting structure.

The nineteenth advantageous feature of the present invention is also toprovide a surface-emitting laser diode array module that includes aplurality of optical fibers and a surface-emitting laser diode arraythat is optically connected to each of the optical fibers. In thissurface-emitting laser diode array module, the surface-emitting laserdiode array being monolithically formed on a substrate, and each deviceof the surface-emitting laser diode array includes: an active layer; aresonator structure including a first distributed Bragg reflector and asecond distributed Bragg reflector that face each other and sandwich theactive layer; a hole passage that extends from a first electrode to theactive layer; an electron passage that extends from a second electrodeto the active layer; a hole restricting structure that is located in thehole passage and defines a region for confining holes to the activelayer; and an optical mode control structure that includes a non-oxideregion provided in the resonator structure and an oxide regionsurrounding the non-oxide region, each region containing Al as aconstituent element, and the area of the non-oxide region being smallerthan the area of the hole restricting structure.

In short, the nineteenth advantageous feature of the present inventionis to provide a surface-emitting laser diode module that employs asurface-emitting laser diode having one of the first through fifteenthadvantageous features or a surface-emitting laser diode array having thesixteenth advantageous feature. The surface-emitting laser diode moduleof the present invention is highly reliable, because thesurface-emitting laser diode employed therein has low device resistance,and can perform high-output operations and achieve single fundamentaltransverse-mode oscillation even with high outputs. A surface-emittinglaser diode or a surface-emitting laser diode array of the presentinvention has a high connecting rate with optical fibers, because of thehigh-output fundamental transverse-mode oscillation. Also, sincehigh-order transverse-mode oscillation is suppressed, it is unlikelythat the optical input to fibers varies with a change of the connectingrate, even if there is a change in the device operation conditions suchas output conditions. Thus, a highly reliable surface-emitting laserdiode module can be provided.

The twentieth advantageous feature of the present invention is toprovide an electrophotographic apparatus that includes a light source,an optical scan system that deflects optical beams emitted from theoptical source, and a photosensor on which optical write is performedwith the optical beams deflected by the optical scan system. In thiselectrophotographic apparatus, the light source includes asurface-emitting laser diode device that includes: an active layer; aresonator structure including a first distributed Bragg reflector and asecond distributed Bragg reflector that face each other and sandwich theactive layer; a hole passage that extends from a first electrode to theactive layer; an electron passage that extends from a second electrodeto the active layer; a hole restricting structure that is located in thehole passage and defines a region for confining holes to the activelayer; and an optical mode control structure that includes a non-oxideregion provided in the resonator structure and an oxide regionsurrounding the non-oxide region, each region containing Al as aconstituent element, and the area of the non-oxide region being smallerthan the area of the hole restricting structure.

The twentieth advantageous feature of the present invention is also toprovide an electrophotographic apparatus-that includes a light source,an optical scan system that deflects optical beams emitted from theoptical source, and a photosensor on which optical write is performedwith the optical beams deflected by the optical scan system. In thiselectrophotographic apparatus, the light source includes asurface-emitting laser diode array that is monolithically formed on asubstrate. Each of the devices that form the surface-emitting laserdiode array includes: an active layer; a resonator structure including afirst distributed Bragg reflector and a second distributed Braggreflector that face each other and sandwich the active layer; a holepassage that extends from a first electrode to the active layer; anelectron passage that extends from a second electrode to the activelayer; a hole restricting structure that is located in the hole passageand defines a region for confining holes to the active layer; and anoptical mode control structure that includes a non-oxide region providedin the resonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element, and the areaof the non-oxide region being smaller than the area of the holerestricting structure.

In short, the twentieth advantageous feature of the present invention isto provide an electrophotographic system that employs, as a WRITE lightsource, a surface-emitting laser diode having one of the first throughfifteenth advantageous features or a surface-emitting laser diode arrayhaving the sixteenth advantageous feature. With the surface-emittinglaser diode that has low device resistance and can perform high-outputoperations and achieve single fundamental transverse-mode oscillationeven with high outputs, a high-definition full-color electrophotographicsystem can be provided. Although a conventional surface-emitting laserdiode has low outputs and is not suitable as a WRITE light source in anelectrophotographic system, a surface-emitting laser diode or asurface-emitting laser diode array of the present invention can achievefundamental transverse-mode oscillation with high outputs, andaccordingly, is suitable as a WRITE light source in anelectrophotographic system. With a surface-emitting laser diode employedas a WRITE light source in an electrophotographic system, it is easy toperform beam shaping, as the outgoing beams each has a circular section.Further, as the positioning accuracy is high in the array, a single lenscan easily concentrate beams with high reproducibility. Accordingly, theoptical system can be simplified, and a high-definition full-colorsystem can be produced at low costs. Also, as a surface-emitting laserdiode of the present invention has high outputs, high-speed write can beperformed with a surface-emitting laser diode array of the presentinvention. Thus, a high-definition full-color electrophotographic systemcan be provided at low costs.

The twenty-first advantageous feature of the present invention is toprovide an optical interconnection system that includes a light source,a light receiving element, and an optical fiber that optically connectsthe light source and the light receiving element. In this opticalinterconnection system, the light source includes a surface-emittinglaser diode device that includes: an active layer; a resonator structureincluding a first distributed Bragg reflector and a second distributedBragg reflector that face each other and sandwich the active layer; ahole passage that extends from a first electrode to the active layer; anelectron passage that extends from a second electrode to the activelayer; a hole restricting structure that is located in the hole passageand defines a region for confining holes to the active layer; and anoptical mode control structure that includes a non-oxide region providedin the resonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element, and the areaof the non-oxide region being smaller than the area of the holerestricting structure.

The twenty-first advantageous feature of the present invention is alsoto provide an optical interconnection system that includes a lightsource, a light receiving element, and an optical fiber that opticallyconnects the light source and the light receiving element. In thisoptical interconnection system, the light source includes asurface-emitting laser diode array that is monolithically formed on asubstrate. Each of the devices that form the surface-emitting laserdiode array includes: an active layer; a resonator structure including afirst distributed Bragg reflector and a second distributed Braggreflector that face each other and sandwich the active layer; a holepassage that extends from a first electrode to the active layer; anelectron passage that extends from a second electrode to the activelayer; a hole restricting structure that is located in the hole passageand defines a region for confining holes to the active layer; and anoptical mode control structure that includes a non-oxide region providedin the resonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element, and the areaof the non-oxide region being smaller than the area of the holerestricting structure.

The twenty-first advantageous feature of the present invention is alsoto provide an optical interconnection system that includes a lightsource, a light receiving element, and an optical fiber that opticallyconnects the light source and the light receiving element. In thisoptical interconnection system, the light source includes asurface-emitting laser diode array that is monolithically formed on asubstrate. Each of the devices that form the surface-emitting laserdiode array includes: an active layer; a resonator structure including afirst distributed Bragg reflector and a second distributed Braggreflector that face each other and sandwich the active layer; a holepassage that extends from a first electrode to the active layer; anelectron passage that extends from a second electrode to the activelayer; a hole restricting structure that is located in the hole passageand defines a region for confining holes to the active layer; and anoptical mode control structure that includes a non-oxide region providedin the resonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element, and the areaof the non-oxide region being smaller than the area of the holerestricting structure. Here, the areas of the non-oxide regions of theoptical mode control structures are different from one another among thedevices that form the surface-emitting laser diode array, andoscillation wavelengths are also different from one another among thedevices.

In short, the twenty-first advantageous feature of the present inventionis to provide an optical interconnection system that employs asurface-emitting laser diode having one of the first through fifteenthadvantageous features or a surface-emitting laser diode array having thesixteenth or seventeenth advantageous feature. As a surface-emittinglaser diode of the present invention has low device resistance and canperform high-output operations while maintaining single fundamentaltransverse-mode oscillation, it is possible to provide a highly reliableoptical interconnection system. A surface-emitting laser diode or asurface-emitting laser diode array of the present invention has a highconnecting rate with optical fibers, because of the high-outputfundamental transverse-mode oscillation. Also, since high-ordertransverse-mode oscillation is suppressed, it is unlikely that theoptical input to fibers varies with a change of the connecting rate,even if there is a change in the device operation conditions such asoutput conditions. Thus, a highly reliable optical interconnectionsystem can be provided.

The twenty-second advantageous feature of the present invention is toprovide an optical communication system that includes a light sourceunit, a light receiving unit, and an optical fiber that opticallyconnects the light source unit and the light receiving unit. In thisoptical communication system, the light source unit includes asurface-emitting laser diode device that includes: an active layer; aresonator structure including a first distributed Bragg reflector and asecond distributed Bragg reflector that face each other and sandwich theactive layer; a hole passage that extends from a first electrode to theactive layer; an electron passage that extends from a second electrodeto the active layer; a hole restricting structure that is located in thehole passage and defines a region for confining holes to the activelayer; and an optical mode control structure that includes a non-oxideregion provided in the resonator structure and an oxide regionsurrounding the non-oxide region, each region containing Al as aconstituent element, and the area of the non-oxide region being smallerthan the area of the hole restricting structure.

The twenty-second advantageous feature of the present invention is alsoto provide an optical communication system that includes a light sourceunit, a light receiving unit, and an optical fiber that opticallyconnects the light source unit and the light receiving unit. In thisoptical communication system, the light source unit includes asurface-emitting laser diode array that is monolithically formed on asubstrate. Each of the devices that form the surface-emitting laserdiode array includes: an active layer; a resonator structure including afirst distributed Bragg reflector and a second distributed Braggreflector that face each other and sandwich the active layer; a holepassage that extends from a first electrode to the active layer; anelectron passage that extends from a second electrode to the activelayer; a hole restricting structure that is located in the hole passageand defines a region for confining holes to the active layer; and anoptical mode control structure that includes a non-oxide region providedin the resonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element, and the areaof the non-oxide region being smaller than the area of the holerestricting structure.

In short, the twenty-second advantageous feature of the presentinvention is to provide an optical communication system that employs asurface-emitting laser diode having one of the first through fifteenthadvantageous features or a surface-emitting laser diode array having thesixteenth advantageous feature. As a surface-emitting laser diode of thepresent invention has low device resistance and can perform high-outputoperations while maintaining single fundamental transverse-modeoscillation, it is possible to provide a highly reliable opticalcommunication system. A surface-emitting laser diode or asurface-emitting laser diode array of the present invention has a highconnecting rate with optical fibers, because of the high-outputfundamental transverse-mode oscillation. Also, since high-ordertransverse-mode oscillation is suppressed, it is unlikely that theoptical input to fibers varies with a change of the connecting rate,even if there is a change in the device operation conditions such asoutput conditions. Furthermore, long-distance communication can beperformed, as higher outputs can be achieved with a surface-emittinglaser diode or a surface-emitting laser diode array of the presentinvention. Thus, a highly reliable optical communication system can beprovided.

The twenty-third advantageous feature of the present invention is toprovide an optical communication system that includes a light sourceunit, a light receiving unit, and an optical fiber that opticallyconnects the light source unit and the light receiving unit. In thisoptical communication system, the light source unit includes asurface-emitting laser diode array that is monolithically formed on asubstrate. Each of the devices that form the surface-emitting laserdiode array includes: an active layer; a resonator structure including afirst distributed Bragg reflector and a second distributed Braggreflector that face each other and sandwich the active layer; a holepassage that extends from a first electrode to the active layer; anelectron passage that extends from a second electrode to the activelayer; a hole restricting structure that is located in the hole passageand defines a region for confining holes to the active layer; and anoptical mode control structure that includes a non-oxide region providedin the resonator structure and an oxide region surrounding the non-oxideregion, each region containing Al as a constituent element, and the areaof the non-oxide region being smaller than the area of the holerestricting structure. Here, the areas of the non-oxide regions of theoptical mode control structures are different from one another among thedevices that form the surface-emitting laser diode array, andoscillation wavelengths are also different from one another among thedevices.

In accordance with the twenty-third advantageous feature of the presentinvention, a highly reliable multi-wave optical communication system inwhich devices can be easily driven can be provided. This opticalcommunication system employs a surface-emitting laser diode array thathas low device resistance, can perform high-output operations inmulti-wave bands, can achieve single fundamental transverse-modeoscillation with high output, and exhibits uniform devicecharacteristics among the devices in the array.

In short, the optical communication system in accordance with thetwenty-third advantageous feature of the present invention employs, as alight source, a multi-wave surface-emitting laser diode array inaccordance with the seventeenth or eighteenth advantageous feature. Insuch a multi-wave surface-emitting laser diode array, thesurface-emitting laser diodes in the array exhibits uniformcharacteristics, and accordingly, high outputs can be achieved. As themulti-wave surface-emitting laser diode array in accordance with theseventeenth or eighteenth advantageous feature exhibits uniformcharacteristics among the surface-emitting laser diodes in the array,high operation reliability can be achieved. Also, as the drive circuitis simple with such a surface-emitting laser diode array, the productioncosts can be lowered. Further, as the device resistance is lower than aconventional device, high-speed modulation can be performed.

The surface-emitting laser diode array in accordance with theseventeenth or eighteenth advantageous feature is suitable especially asa light source in a wavelength division multiplexing communicationsystem, as the wavelengths of the surface-emitting laser diodes in thearray are different from one another. In wavelength divisionmultiplexing communication, optical signals of different wavelengths aretransmitted through a single fiber, so as to realize high-speedlarge-capacity communication.

In view of the above facts, an optical communication system that employsa multi-wave surface-emitting laser diode array of the present inventionis highly reliable and can perform high-speed communication.

The twenty-fourth advantageous feature of the present invention is toprovide a method of fabricating a surface-emitting laser diode devicethat includes: an active layer; a resonator structure including a firstdistributed Bragg reflector and a second distributed Bragg reflectorthat face each other and sandwich the active layer; a hole passage thatextends from a first electrode to the active layer; an electron passagethat extends from a second electrode to the active layer; a holerestricting structure that is located in the hole passage and includes anon-oxide region that defines a region for confining holes to the activelayer, and an oxide region surrounding the non-oxide region, each regioncontaining Al as a constituent element; and an optical mode controlstructure that includes a non-oxide region provided in the resonatorstructure and an oxide region surrounding the non-oxide region, eachregion containing Al as a constituent element, and the area of thenon-oxide region being smaller than the area of the hole restrictingstructure. This method includes the steps of: forming the holerestricting structure including the oxide region and the non-oxideregion by selectively oxidizing a semiconductor layer that contains Alas a constituent element; and forming the optical mode control structureincluding the oxide region and the non-oxide region by selectivelyoxidizing a semiconductor layer that contains Al as a constituentelement. In this method, the step of forming the hole restrictingstructure and the step of forming the optical mode control structure areperformed simultaneously, and the thickness of the semiconductor layerthat is to form the hole restricting structure and contains Al as aconstituent element is different from the thickness of the semiconductorlayer that is to form the optical mode control structure and contains Alas a constituent element.

In accordance with the twenty-fourth advantageous feature of the presentinvention, a hole restricting structure and an optical mode controlstructure including non-oxide regions having different areas are formedout of a selectively oxidized semiconductor layer having a firstthickness and a selectively oxidized semiconductor layer having a secondthickness, respectively, in a method of fabricating a surface-emittinglaser diode having one of the first through eleventh advantageousfeatures.

By this method, a surface-emitting laser diode that has low deviceresistance and can perform high-output operations while maintainingsingle fundamental transverse-mode oscillation can be easily producedwith high controllability. In a surface-emitting laser diode produced inaccordance with the twenty-fourth advantageous feature of the presentinvention, selective oxidation structures including non-oxide regionshaving different areas can be formed in the device through a one-timeoxidation process, by virtue of the difference in the oxidation speedcaused by the thickness difference between the semiconductor mixedcrystals each containing Al.

Accordingly, a surface-emitting laser diode of the present invention canbe produced, without any special step added to the conventionalproduction procedures. Thus, a high-performance device that can achievesingle transverse-mode oscillation with high outputs can be produced atthe same costs as the conventional production costs.

The twenty-fifth advantageous feature of the present invention is toprovide a method of fabricating a surface-emitting laser diode devicethat includes: an active layer; a resonator structure including a firstdistributed Bragg reflector and a second distributed Bragg reflectorthat face each other and sandwich the active layer; a hole passage thatextends from a first electrode to the active layer; an electron passagethat extends from a second electrode to the active layer; a holerestricting structure that is located in the hole passage and includes anon-oxide region that defines a region for confining holes to the activelayer, and an oxide region surrounding the non-oxide region, each regioncontaining Al as a constituent element; and an optical mode controlstructure that includes a non-oxide region provided in the resonatorstructure and an oxide region surrounding the non-oxide region, eachregion containing Al as a constituent element, and the area of thenon-oxide region being smaller than the area of the hole restrictingstructure. This method includes the steps of: forming the holerestricting structure including the oxide region and the non-oxideregion by selectively oxidizing a semiconductor layer that contains Alas a constituent element; and forming the optical mode control structureincluding the oxide region and the non-oxide region by selectivelyoxidizing a semiconductor layer that contains Al as a constituentelement. In this method, the step of forming the hole restrictingstructure and the step of forming the optical mode control structure areperformed simultaneously, and the Al composition of the semiconductorlayer that is to form the hole restricting structure and contains Al asa constituent element is different from the Al composition of thesemiconductor layer that is to form the optical mode control structureand contains Al as a constituent element.

In accordance with the twenty-fifth advantageous feature of the presentinvention, a hole restricting structure and a high-order transverse-modesuppressing layer including non-oxide regions having different areas areformed out of a selectively oxidized semiconductor layer having a firstAl composition and a selectively oxidized semiconductor layer having asecond Al composition, respectively, in a method of fabricating asurface-emitting laser diode having one of the first through eleventhadvantageous features. By this method, a surface-emitting laser diodethat has low device resistance and can perform high-output operationswhile maintaining single fundamental transverse-mode oscillation can beeasily produced with high controllability. In a surface-emitting laserdiode produced in accordance with the twenty-fifth advantageous featureof the present invention, oxidation confinement structures of differentsizes can be formed in the device through a one-time oxidation process,by virtue of the difference in the oxidation speed caused by the Alcomposition difference between the semiconductor mixed crystals eachcontaining Al.

Accordingly, a surface-emitting laser diode of the present invention canbe produced, without any special step added to the conventionalproduction procedures. Thus, a high-performance device that can achievesingle transverse-mode oscillation with high outputs can be produced atthe same costs as the conventional production costs.

The twenty-sixth advantageous feature of the present invention is toprovide a method of fabricating a surface-emitting laser diode devicethat includes: an active layer; a resonator structure including a firstdistributed Bragg reflector and a second distributed Bragg reflectorthat face each other and sandwich the active layer; a hole passage thatextends from a first electrode to the active layer; an electron passagethat extends from a second electrode to the active layer; a holerestricting structure that is located in the hole passage and includes anon-oxide region that defines a region for confining holes to the activelayer, and an oxide region surrounding the non-oxide region, each regioncontaining Al as a constituent element; and an optical mode controlstructure that includes a non-oxide region provided in the resonatorstructure and an oxide region surrounding the non-oxide region, eachregion containing Al as a constituent element, and the area of thenon-oxide region being smaller than the area of the hole restrictingstructure. This method includes the steps of: forming a first mesa thatincludes a semiconductor layer that contains Al as a constituent elementand is to form, through selective oxidation, the hole restrictingstructure including the oxide region and the non-oxide region; forming asecond mesa that includes a semiconductor layer that contains Al as aconstituent element and is to form, through selective oxidation, theoptical mode control structure including the oxide region and thenon-oxide region; forming the hole restricting structure including theoxide region and the non-oxide region by selectively oxidizing thesemiconductor layer that contains Al as a constituent element; andforming the optical mode control structure including the oxide regionand the non-oxide region by selectively oxidizing the semiconductorlayer that contains Al as a constituent element. In this method, thestep of forming the hole restricting structure and the step of formingthe optical mode control structure are performed simultaneously, and thesize of the first mesa is different from the size of the second mesa.

In accordance with the twenty-sixth advantageous feature of the presentinvention, a hole restricting layer and an optical mode controlstructure including non-oxide regions having different areas are formedby a first mesa that has a first mesa size and includes a high-ordertransverse-mode suppressing layer, and a second mesa that has a secondmesa size, different from the first mesa size, and includes a holerestricting structure, respectively, in a method of fabricating asurface-emitting laser diode having one of the first through eleventhadvantageous features. By this method, a surface-emitting laser diodethat has low device resistance and can perform high-output operationswhile maintaining single fundamental transverse-mode oscillation can beeasily produced with high controllability at low costs.

In the method in accordance with the twenty-sixth advantageous featureof the present invention, the size of the mesa that includes the opticalmode control structure differs from the size of the mesa that includesthe hole restricting structure. More specifically, the size of the mesathat includes the hole restricting structure is made greater than thesize of the mesa that includes the optical mode control structure, sothat the non-oxide region of the hole restricting structure has a largerarea than the non-oxide region of the optical mode control structureafter oxidation of the selectively oxidized layers at the same oxidationrates.

Accordingly, a surface-emitting laser diode of the present invention canbe produced, without any special step added to the conventionalproduction procedures. Thus, a high-performance device that can achievesingle transverse-mode oscillation with high outputs can be produced atthe same costs as the conventional production costs. This method inaccordance with the twenty-sixth advantageous feature of the presentinvention is suitable especially for fabricating a surface-emittinglaser diode of an intra-cavity contact type.

The twenty-seventh advantageous feature of the present invention is toprovide a method of fabricating a surface-emitting laser diode arraythat is formed with devices each including: an active layer; a resonatorstructure including a first distributed Bragg reflector and a seconddistributed Bragg reflector that face each other and sandwich the activelayer; a hole passage that extends from a first electrode to the activelayer; an electron passage that extends from a second electrode to theactive layer; a hole restricting structure that is located in the holepassage and includes a non-oxide region that defines a region forconfining holes to the active layer, and an oxide region surrounding thenon-oxide region, each region containing Al as a constituent element;and an optical mode control structure that includes a non-oxide regionprovided in the resonator structure and an oxide region surrounding thenon-oxide region, each region containing Al as a constituent element,the area of the non-oxide region being smaller than the area of the holerestricting structure, the areas of the non-oxide regions of the opticalmode control structures being different from one another among thedevices that form the surface-emitting laser diode array, andoscillation wavelengths being also different from one another among thedevices. This method includes the steps of: forming a first mesa thatincludes a semiconductor layer that contains Al as a constituent elementand is to form, through selective oxidation, the hole restrictingstructure including the oxide region and the non-oxide region; forming asecond mesa that includes a semiconductor layer that contains Al as aconstituent element and is to form, through selective oxidation, theoptical mode control structure including the oxide region and thenon-oxide region; forming the hole restricting structure including theoxide region and the non-oxide region by selectively oxidizing thesemiconductor layer that contains Al as a constituent element; andforming the optical mode control structure including the oxide regionand the non-oxide region by selectively oxidizing the semiconductorlayer that contains Al as a constituent element. In this method, thestep of forming the hole restricting structure and the step of formingthe optical mode control structure are performed simultaneously, and thesizes of the second mesas are different from one another among thedevices that have different wavelengths from one another.

In accordance with the twenty-seventh advantageous feature of thepresent invention, the sizes of the mesas each including an optical modecontrol structure are varied so as to form non-oxide regions havingdifferent areas in a method of fabricating a multi-wave surface laserdiode array having the seventeenth advantageous feature. Thus, asurface-emitting laser diode array that has low device resistance, canperform high-output operations while maintaining single fundamental modeoscillation, and exhibits uniform device characteristics, can be easilyproduced with high controllability at low costs.

In short, in the method in accordance with the twenty-seventhadvantageous feature of the present invention, the sizes of the mesaseach including an optical mode control structure are varied in amulti-wave surface-emitting laser diode array having the seventeenthadvantageous feature.

As the in-plane oxidation speeds of the optical mode control structuresare uniform, the sizes of the non-oxide regions each remaining at thecenter of each corresponding mesa can be varied by varying the sizes ofthe mesas. Also, in the method in accordance with the twenty-seventhfeature of the present invention, surface-emitting laser diodesincluding non-oxide regions having different areas can be produced by aone-time oxidation process. Thus, a multi-wave surface-emitting laserdiode array of the present invention can be easily produced at the samecosts as the conventional production costs.

The following is a description of embodiments of the present invention.

First Embodiment

A first embodiment of the present invention is a surface-emitting laserdiode device that includes an active layer, a pair of distributed Braggreflectors between which the active layer is interposed, a hole passagethat extends from a first electrode to the active layer, and an electronpassage that extends from a second electrode to the active layer.

This surface-emitting laser diode device is characterized by including:a hole restricting structure that includes a non-oxide region and anoxide region formed by selectively oxidizing a semiconductor layer(selectively oxidized layer) containing Al as a constituent element inthe hole passage, and defines the region for confining holes to theactive layer: and an optical mode control structure that includes anon-oxide region and an oxide region formed by selectively oxidizing asemiconductor layer (selectively oxidized layer) containing Al as aconstituent element. In this surface-emitting laser diode device, thenon-oxide region of the optical mode control structure has a smallerarea than the non-oxide region (the hole restricting area) of the holerestricting structure.

With this structure, it is possible to perform hole restriction andsingle fundamental transverse-mode control, which are conventionallyperformed by a single selective oxidation structure, with differentselective oxidation structures. Thus, an optimum structure can beachieved for the hole restriction and the single fundamentaltransverse-mode control. In this device, the hole restricting structuredoes not need to suppress the high-order transverse mode, and can have alarge-area non-oxide region to prevent a rapid increase of the deviceresistance. Also, since the restricting rate of holes is high, the areaof the non-oxide region of the hole restricting structure can be madelarge. Thus, the holes can be restricted to the center of the mesa inthe active layer region, and a high internal quantum efficiency can beachieved.

Also, the optical mode control structure that is provided as well as thehole restricting structure and has the selective oxidation structureincluding a relatively small-area non-oxide region is optimallydesigned, being provided in a region having less influence on theresistance. This surface-emitting laser diode device thus caneffectively suppress high-order transverse-mode oscillation, without arapid increase of the device resistance.

Second Embodiment

A second embodiment of the present invention is a surface-emitting laserdiode having the same structure as the surface-emitting laser diode ofthe first embodiment, except that the surface-emitting laser diode ofthis embodiment has the optical mode control structure in the electronpassage. The optical mode control structure has a non-oxide regionsmaller than the area of the non-oxide region of the hole restrictingstructure.

With this structure of the second embodiment, the optical mode controlstructure that is located in the electron passage and is formed by aselective oxidation structure including the smaller non-oxide region caneffectively suppress high-order transverse-mode oscillation, without arapid increase of device resistance.

Also, the hole restricting structure that is located in the hole passageand is formed by the selective oxidation structure including the largernon-oxide region can restrict holes to the center of the mesa in theactive layer region and achieve a high internal quantum efficiency,without a rapid increase of device resistance.

Third Embodiment

A third embodiment of the present invention is a surface-emitting laserdiode having the same structure as the surface-emitting laser diode ofthe first embodiment, except that the surface-emitting laser diode ofthis embodiment has the optical mode control structure in a region thatdoes not meet both the electron passage and the hole passage. Theoptical mode control structure has a non-oxide region that is smallerthan the area of the non-oxide region in the hole restricting structure.

With this structure of the third embodiment, the optical mode controlstructure that is provided in a region that does not meet the electronand hole passages and is formed by a selective oxidation structureincluding the smaller non-oxide region can effectively suppresshigh-order transverse-mode oscillation, without a rapid increase ofdevice resistance.

Also, the hole restricting structure that is located in the hole passageand is formed by the selective oxidation structure including the largernon-oxide region can restrict holes to the center of the mesa in theactive layer region and achieve a high internal quantum efficiency,without a rapid increase of device resistance.

Fourth Embodiment

A fourth embodiment of the present invention is a surface-emitting laserdiode having the same structure as the surface-emitting laser diode ofthe third embodiment, except that the semiconductor layer (a selectivelyoxidized layer) that contains Al as a constituent element and forms thehole restricting structure through selective oxidation is a p-typelayer. The hole restricting structure is located in the hole passage.

Like the structure of the third embodiment, the location of the holerestricting structure in the hole passage can be in a semiconductordistributed Bragg reflector or a resonator spacer layer. However, aresonance region (or a resonator spacer layer) is normally a non-dopedregion (layer). If a non-doped selectively oxidized layer is provided insuch a resonance region, the resistance becomes very high due tooxidation restriction. Therefore, a p-type layer is used as aselectively oxidized layer that forms the hole restricting structure inthe hole passage. With this structure, holes in the active layer regioncan be restricted to the center of the mesa, and a high internal quantumefficiency can be achieved.

Also, the optical mode control structure that is provided in a regionoutside the electron passage and the hole passage and is formed by theselective oxidation structure including the smaller non-oxidized areacan effectively suppress high-order transverse-mode oscillation, withoutan increase of device resistance.

Fifth Embodiment

A fifth embodiment of the present invention is a surface-emitting laserdiode having the same structure as the surface-emitting laser diode ofthe second embodiment, except that the semiconductor layer (aselectively oxidized layer) that forms the hole restricting structure inthe hole passage through selective oxidation and contains Al as aconstituent element is a p-type layer, and that the semiconductor layer(a selectively oxidized layer) that forms the optical mode controlstructure in the electron passage through selective oxidation is ann-type layer.

The locations of the hole restricting structure and the optical modecontrol structure can be in a semiconductor distributed Bragg reflectoror a resonator spacer layer. However, a resonance region (or a resonatorspacer layer) is normally a non-doped region (layer). If a non-dopedselectively oxidized layer is provided in such a resonance region, theresistance becomes very high due to oxidation restriction. Therefore, ap-type layer is used as a selectively oxidized layer that forms the holerestricting structure in the hole passage, and an n-type layer is usedas a selectively oxidized layer that forms the optical mode controlstructure in the electron passage. With this structure, the resistanceof the respective carriers can be effectively reduced.

In the structure of the fifth embodiment, the selective oxidationstructure that is provided in the hole passage and has the largernon-oxide region can restrict holes to the center of the mesa in theactive region, and achieve a high internal quantum efficiency, whilemaintaining the device resistance very low.

Also, the optical mode control structure that is provided in theelectron passage and is formed by the selective oxidation structureincluding the smaller non-oxidized area can effectively suppresshigh-order transverse-mode oscillation, while maintaining the deviceresistance very low.

Sixth Embodiment

A sixth embodiment of the present invention is a surface-emitting laserdiode that has the same structure as one of the surface-emitting laserdiodes of the first through fifth embodiments, except that the pair ofdistributed Bragg reflectors is made of semiconductor materials.

With this structure of the sixth embodiment, any of the devices of thefirst through fifth embodiments can be obtained through a one-timecrystal growth process with high precision. Furthermore, each device canbe manufactured through a semiconductor process with highcontrollability, at a high yield rate.

Seventh Embodiment

A seventh embodiment of the present invention is a surface-emittinglaser diode that has the same structure as one of the surface-emittinglaser diodes of the first through fifth embodiments, except that one ofthe distributed Bragg reflectors is made of a semiconductor materialwhile the other one is made of a dielectric material.

With this structure of the seventh embodiment that employs a dielectricreflector with a small absorption loss, a highly efficientsurface-emitting laser diode can be obtained.

Eighth Embodiment

An eighth embodiment of the present invention is a surface-emittinglaser diode that has the same structure as one of the surface-emittinglaser diodes of the first through seventh embodiments, except that atleast one of the distributed Bragg reflectors is a n-type semiconductordistributed Bragg reflector, and that a tunnel junction is providedbetween the n-type semiconductor distributed Bragg reflector and theactive layer.

With this structure of the eighth embodiment that employs an n-typesemiconductor distributed Bragg reflector with a small absorption loss,instead of a p-type semiconductor distributed Bragg reflector, a highlyefficient surface-emitting laser diode can be obtained.

Ninth Embodiment

A ninth embodiment of the present invention is a surface-emitting laserdiode that has the same structure as one of the surface-emitting laserdiodes of the first through eighth embodiments, except that at least oneof the distributed Bragg reflectors is a non-doped semiconductordistributed Bragg reflector or a Bragg reflector partially including aregion formed by a non-doped semiconductor distributed Bragg reflector,and that an electrode for confining carriers is provided on asemiconductor layer between the active layer and the non-dopedsemiconductor distributed Bragg reflector or the region formed by anon-doped semiconductor Bragg reflector.

With this structure of the ninth embodiment that employs a non-dopedsemiconductor distributed Bragg reflector with a small absorption loss,a highly efficient surface-emitting laser diode can be obtained.

Tenth Embodiment

A tenth embodiment of the present invention is a surface-emitting laserdiode having the same structure as one of the surface-emitting laserdiodes of the first through ninth embodiments, except that the holerestricting structure in the hole passage is provided at a locationcorresponding to an antinode of the standing wave of oscillating light.

With this structure of the tenth embodiment, the optical mode controlstructure formed by the selective oxidation structure provided at alocation corresponding to an antinode of the standing wave ofoscillating light can retrain high-order transverse-mode oscillationwith greater effect.

Eleventh Embodiment

An eleventh embodiment of the present invention is a surface-emittinglaser diode having the same structure as one of the surface-emittinglaser diodes of the first through tenth embodiments, except that two ormore optical mode control structures are provided in the electronpassage or in a region that does not meet the electron and holepassages.

With this structure of the eleventh embodiment, the optical mode controlstructures that are provided in the electron passage or in a regionoutside the electron and hole passages and are formed by selectiveoxidation structures each having a smaller non-oxide region can retrainhigh-order transverse-mode oscillation with greater effect.

Twelfth Embodiment

A twelfth embodiment of the present invention is a surface-emittinglaser diode having the same structure as one of the surface-emittinglaser diodes of the first through eleventh embodiments, except that thesemiconductor layer (a selectively oxidized layer) that contains Al as aconstituent element and forms the optical mode control structure throughselective oxidation in the electron passage or in a region outside theelectron and hole passages is thicker than the semiconductor layer (aselectively oxidized layer) that contains Al as a constituent elementand forms the hole restricting structure through selective oxidation inthe hole passage.

This structure of the twelfth embodiment readily realizes asurface-emitting laser diode of the present invention with highcontrollability.

Thirteenth Embodiment

A thirteenth embodiment of the present invention is a surface-emittinglaser diode having the same structure as one of the surface-emittinglaser diodes of the first through eleventh embodiments, except that theAl content of the semiconductor layer (a selectively oxidized layer)that contains Al as a constituent element and forms the optical modecontrol structure through selective oxidation in the electron passage orin a region outside the electron and hole passages is greater than theAl content of the semiconductor layer (a selectively oxidized layer)that contains Al as a constituent element and forms the hole restrictingstructure through selective oxidation in the hole passage.

This structure of the thirteenth embodiment readily realizes asurface-emitting laser diode of the present invention with highcontrollability.

Fourteenth Embodiment

A fourteenth embodiment of the present invention is a surface-emittinglaser diode having the same structure as one of the surface-emittinglaser diodes of the first through eleventh embodiments, except that theactive layer contains at least one III-group element selected from thegroup of Al, Ga, and In, and at least one V-group element selected fromthe group of As and P, and that the oscillation wavelength is shorterthan 1.1 μm.

This structure of the fourteenth embodiment realizes a device that hasthe oscillation wavelength in a short-wave band area and can effectivelyachieve single fundamental transverse-mode oscillation with highoutputs.

Fifteenth Embodiment

A fifteenth embodiment of the present invention is a surface-emittinglaser diode having the same structure as one of the surface-emittinglaser diodes of the first through eleventh embodiments, except that theactive layer contains at least one III-group element selected from thegroup of Ga and In, and at least one V-group element selected from thegroup of As, P, N, and Sb, and that the oscillation wavelength is longerthan 1.1 μm.

This structure of the fifteenth embodiment realizes a device that hasthe oscillation wavelength in a long-wave band area and exhibits highefficiency.

The device of the fifteenth embodiment has excellent temperaturecharacteristics, and is suitable for a light source in opticalcommunication.

Sixteenth Embodiment

A sixteenth embodiment of the present invention is a surface-emittinglaser diode array that is formed by surface-emitting laser diodes of oneof the first through fifteenth embodiments of the present invention.

As the surface-emitting laser diode array of the sixteenth embodiment isformed by surface-emitting laser diodes of one of the first throughfifteenth embodiments, the resistance can remain very low. Thus, asurface-emitting laser diode array that can achieve single fundamentaltransverse-mode oscillation while having high outputs can be provided.

Seventeenth Embodiment

A seventeenth embodiment of the present invention is a surface-emittinglaser diode array having the same structure as the surface-emittinglaser diode array of the sixteenth embodiment, except that two or moretypes of surface-emitting laser diodes are employed. Thesurface-emitting laser diodes that form the surface-emitting laser diodearray of this embodiment have different oscillation wavelengths, as theareas of the non-oxide regions of the optical mode control structuresare different from one another among the surface-emitting laser diodes.

It is known that the resonance wavelength of the resonator varies withthe area of the non-oxide region of the selective oxidation structure inan oxidation-restricting surface-emitting laser diode. Accordingly, theoscillation wavelength (the resonance wavelength) becomes shorter, asthe area of a non-oxide region becomes smaller. The reason that a changeof the wavelength is caused by a change of the area of the non-oxideregion is that, since the oxide region has a confining effect on thetransverse-mode oscillation, the transverse-mode extent changes with achange of the area of the non-oxide region, and the resonance conditionsof the resonator in the vertical direction change.

For instance, a change of the oscillation wavelength (resonancewavelength) to a shorter wavelength with respect to the area of thenon-oxide region of each device in a 0.98 μm band was estimated by anumerical calculation in “IEEE Journal of Selected Topics in QuantumElectronics Vol. 3, No. 2, page 344, 1997” and “IEEE Journal of QuantumElectronics Vol. 34, No. 10, p. 1890, 1998”. The results in thesereferences show that the oscillation wavelength started shifting to ashorter wavelength when the diameter of the non-oxide region was 5 μm,and the shifting became rapid when the diameter of the non-oxide regionwas 2 μm or shorter.

Also, “IEEE Photonics Technology Letter Vol. 8, No. 7, p. 858, 1996”reports a case in which devices including non-oxide regions havingdifferent areas were produced to actually form a 2×2 surface-emittinglaser diode array having 1 nm wavelength intervals in a 0.98 μm. Thesmallest size of the restricting region here was 2.0 μm, and the largestsize was 3.5 μm.

However, with conventional surface-emitting laser diodes each performinghole restriction and high-order transverse-mode control with oneselective oxidation structure, there is a problem that the thresholdcurrent and optical outputs greatly vary within the array, due to thevaried sizes of the oxidation confinement structures. Furthermore, adecrease of the size of an oxidation confinement structure drasticallyincreases the resistance in the restricting region, and accordingly, itbecomes difficult to have high outputs due to heat generation. Actually,the above document discloses that even the device with the largestoxidation restriction structure of 3.5 μm had the highest optical outputof only 0.38 mW due to heat generation of the device. It can beconsidered that the devices with the smaller oxidation confinementstructures had even lower optical outputs due to heat generation causedby increases of resistance. In view of these facts, conventional devicescannot form a multi-wave surface-emitting laser diode array thatperforms high-output operations.

Also, to obtain a multi-wave surface-emitting laser diode array that hasa broader band area, it is necessary to form even smaller non-oxideregions. If the diameter of a non-oxide region is 1 μm or shorter inpractice, light loss caused by the selective oxidation structure shouldbe very large. Therefore, it should be considered that a diameter of 1μm is the smallest possible size for non-oxide regions that can beactually used. If the non-oxide regions of conventional devices are madeas small as this, the heat generation (the device resistance) rapidlyincreases, and it becomes very difficult to achieve oscillation.

On the other hand, a multi-wave surface-emitting laser diode array thatemploys surface-emitting laser diodes of the present invention caneasily solve the above problems. First of all, a hole restrictingstructure and an optical mode control structure are provided separatelyfrom each other in each surface-emitting laser diode of the presentinvention. Furthermore, the optical mode control structure is providedin an n-type semiconductor layer that rarely increases the resistance,or in a region that does not meet the carrier (electron and hole)passages and does not affect the electric resistance. Accordingly, aresistance increase caused by a decrease of the area of the non-oxideregion of the optical mode control structure is smaller than in aconventional device. In the case of the optical mode control structurelocated outside the carrier passages, there are no resistance increasesat all. With this structure, heat generation due to a resistanceincrease can have only a very limited influence. Accordingly, devicesthat include optical mode control structures having small non-oxideregions can achieve fundamental transverse-mode oscillation with highoutputs. Also, optical outputs can be made uniform among devices.Further, the non-oxide regions of the hole restricting structures of thedevices in the array have the same areas, so that the devicecharacteristics such as the oscillation threshold current and theoperation voltage can be made uniform in the array.

As described above, the surface-emitting laser diode array of theseventeenth embodiment functions as a multi-wave surface-emitting laserdiode array that exhibits uniform device characteristics and can performhigh-output operations.

Eighteenth Embodiment

An eighteenth embodiment of the present invention is a surface-emittinglaser diode array having the same structure as the surface-emittinglaser diode array of the seventeenth embodiment, except that each of thesurface-emitting laser diodes that form the surface-emitting laser diodearray includes two or more optical mode control structures.

With the two or more optical mode control structures, thetransverse-mode light confining effect is increased. Thus, oscillationwavelengths (resonance wavelengths) can be more effectively madeshorter.

Nineteenth Embodiment

A nineteenth embodiment of the present invention is a surface-emittinglaser diode module in which the surface-emitting laser diode of one ofthe first through fifteenth embodiments or the surface-emitting laserdiode array of the sixteenth embodiment is employed.

With the surface-emitting laser diode of one of the first throughfifteenth embodiments or the surface-emitting laser diode array of thesixteenth embodiment, single fundamental transverse-mode oscillation canbe steadily obtained with high outputs. Accordingly, the connection ratewith the fibers of the surface-emitting laser diode module, in which thesurface-emitting laser diode of one of the first through fifteenthembodiments or the surface-emitting laser diode array of the sixteenthembodiment is employed, rarely fluctuates. Thus, a highly reliablesurface-emitting laser diode array module can be obtained.

Twentieth Embodiment

A twentieth embodiment of the present invention is anelectrophotographic system in which the surface-emitting laser diode ofone of the first-through fifteenth embodiments or the surface-emittinglaser diode array is employed.

With the surface-emitting laser diode of one of the first throughfifteenth embodiments or the surface-emitting laser diode array of thesixteenth embodiment, single fundamental transverse-mode oscillation canbe steadily obtained with high outputs. As outgoing beams have circularshapes and exhibit high positioning precision in the array, a singlelens can easily concentrate beams with high reproducibility.Accordingly, the optical system can be simplified, and anelectrophotographic system can be provided at low costs. Also, as thearray can achieve high outputs with the single transverse mode,high-speed write can be performed. Thus, a high-speedelectrophotographic system can be provided.

Twenty-First Embodiment

A twenty-first embodiment of the present invention is an opticalinterconnection system in which the surface-emitting laser diode of oneof the first through fifteenth embodiments or the surface-emitting laserdiode array of the sixteenth embodiment is employed.

With the surface-emitting laser diode of one of the first throughfifteenth embodiments or the surface-emitting laser diode array of thesixteenth embodiment, single fundamental transverse-mode oscillation canbe steadily obtained with high outputs. Also, the connection withoptical fibers is tight, and the transverse-mode oscillation wavelengthrarely fluctuates with any change in the device operation conditions.Thus, a highly reliable optical interconnection system can be provided.

Twenty-Second Embodiment

A twenty-second embodiment of the present invention is an opticalcommunication system in which the surface-emitting laser diode of one ofthe first through fifteenth embodiments or the surface-emitting laserdiode array of the sixteenth embodiment is employed.

With the surface-emitting laser diode of one of the first throughfifteenth embodiments or the surface-emitting laser diode array of thesixteenth embodiment, single fundamental transverse-mode oscillation canbe steadily obtained with high outputs. Also, the connection withoptical fibers is tight, and the transverse-mode oscillation wavelengthrarely fluctuates with any change in the device operation conditions.Thus, a highly reliable optical communication system can be provided.Furthermore, it is possible to achieve high outputs in the fundamentaltransverse mode. Thus, an optical communication system that performslong-distance communications can be provided.

Twenty-Third Embodiment

A twenty-third embodiment of the present invention is an opticalcommunication system in which the surface-emitting laser diode array ofthe seventeenth or eighteenth embodiment.

In the surface-emitting laser diode array of the seventeenth oreighteenth embodiment, the surface-emitting laser diodes have uniformcharacteristics. Accordingly, drive control can be easily performed onthe surface-emitting laser diode array. With the multi-wavesurface-emitting laser diode array that can perform high-outputoperations in the single fundamental transverse mode, a highly reliableoptical communication system can be provided at low costs.

Twenty-Fourth Embodiment

A twenty-fourth embodiment of the present invention is a method offabricating the surface-emitting laser diode of any of the first througheleventh embodiments. This method is characterized by the steps offorming a hole restricting structure out of a selectively oxidizedsemiconductor layer having a first thickness, and forming an opticalmode control structure out of a selectively oxidized semiconductor layerhaving a second thickness that is different from the first thickness.The non-oxide regions of the hole restricting structure and the opticalmode control structure have different areas from each other.

By this method of the twenty-fourth embodiment, the surface-emittinglaser diode of any of the first through eleventh embodiments can beeasily obtained with high controllability and high yields.

Twenty-Fifth Embodiment

A twenty-fifth embodiment of the present invention is a method offabricating the surface-emitting laser diode of any of the first througheleventh embodiments. This method is characterized by the steps offorming a hole restricting structure out of a selectively oxidizedsemiconductor layer having a first Al composition, and forming anoptical mode control structure out of a selectively oxidizedsemiconductor layer having a second Al composition that is differentfrom the first Al composition. The non-oxide regions of the holerestricting structure and the optical mode control structure havedifferent areas from each other.

By this method of the twenty-fifth embodiment, the surface-emittinglaser diode of any of the first through eleventh embodiments can beeasily obtained with high controllability and high yields.

Twenty-Sixth Embodiment

A twenty-sixth embodiment of the present invention is a method offabricating the surface-emitting laser diode of any of the first througheleventh embodiments. This method is characterized by the steps offorming a first mesa that has a first mesa size and includes an opticalmode control structure, and forming a second mesa that has a second mesasize, different from the first mesa size, and includes a holerestricting structure. The areas of the non-oxide regions of the holerestricting structure and the optical mode control structure aredifferent from each other.

By this method of the twenty-sixth embodiment, the surface-emittinglaser diode of any of the first through eleventh embodiments can beeasily obtained with high controllability and high yields.

Twenty-Seventh Embodiment

A twenty-seventh embodiment of the present invention is a method offabricating the surface-emitting laser diode array of the seventeenth oreighteenth embodiment. This method is characterized by the step offorming mesas that include high-order transverse-mode control layers andhave different mesa sizes among the surface-emitting laser diodes in thesurface-emitting laser diode array. With the mesa size variation,non-oxide regions having different areas are formed.

By this method of the twenty-seventh embodiment, the multi-wavesurface-emitting laser diode array of the seventeenth or eighteenthembodiment can be easily provided with high controllability and highyields, without an increase in the number of production procedures.

EXAMPLES

The following is a description of specific examples of the presentinvention, with reference to the accompanying drawings.

Example 1

FIG. 1 illustrates a surface-emitting laser diode of Example 1 of thepresent invention.

The surface-emitting laser diode shown in FIG. 1 is a 0.85 μmsurface-emitting laser diode having a GaAs/Al_(0.15)Ga_(0.85)Asmulti-quantum well structure as an active layer. The structure of thissurface-emitting laser diode will be described below, in conjunctionwith the fabrication procedures.

The surface-emitting laser diode shown in FIG. 1 does crystal growth bya metal organic chemical vapor deposition (MOCVD) technique. In thissurface-emitting laser diode, trimethylaluminum (TMA), trimethylgallium(TMG), trimethylindium (TMI), are utilized as III-group raw materials.As a V-group raw material, an arsine (AsH₃) gas is used. Further, CBr₄is employed as a p-type dopant, and H₂Se is employed as an n-typedopant.

More specifically, the device shown in FIG. 1 includes an n-GaAssubstrate 101, an n-GaAs buffer layer 102, a 36-periodn-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 103 having then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As as one period, a non-dopeAl_(0.15)Ga_(0.85)As resonator spacer 105, a GaAs/Al_(0.15)Ga_(0.85)Asmulti-quantum well active layer 106, a non-dope Al_(0.15)Ga_(0.85)Asresonator spacer 107, and a 20-periodp-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 108. These layers are formed through crystalgrowth in this order, with the substrate 101 being at the bottom.Further, a contact layer (not shown) having a high-density p-type dopant(carbon) near the surface is provided in the Al_(0.15)Ga_(0.85)As layerthat is the outermost surface layer of the upper semiconductordistribution plug reflector 108.

The n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 103 and thep-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 108 are provided with an n-AlAs selectivelyoxidized layer 104 and a p-AlAs selectively oxidized layer 109,respectively. The selectively oxidized layers 104 and 109 each includesan oxidized area 112 (shown in black in FIG. 1, the same applying to thefollowing examples) that is selectively oxidized and a non-oxide area113 a/113 b that is not oxidized.

Here, an n-Al_(0.9)Ga_(0.1)As layer 103 a that is the low refractionlayer of the lower semiconductor distributed Bragg reflector 103, ap-Al_(0.9)Ga_(0.1)As layer 108 a that is the low refraction layer of theupper semiconductor distributed Bragg reflector 108, ann-Al_(0.15)Ga_(0.85)As layer 103 b that is the high refraction layer ofthe lower semiconductor distributed Bragg reflector 103, and ap-Al_(0.15)Ga_(0.85)As layer 108 b that is the high refraction layer ofthe upper semiconductor distributed Bragg reflector 108, each has such afilm thickness that the phase change of the oscillating light in eachsemiconductor layer becomes π/2, which satisfies the phase conditionsfor multiple reflection of the distributed Bragg reflectors (each of thelayers is shown in FIG. 2). More specifically, the Al_(0.9)Ga_(0.1)Aslayers 103 a and 108 a are each 69.8 nm thick, and theAl_(0.15)Ga_(0.85)As layers 103 b and 108 b are each 59.7 nm thick.

FIG. 2 illustrates the resonance region (the resonator region) of thesurface-emitting-laser diode of FIG. 1, in conjunction with the standingwave of the oscillating light. Hereinafter, the resonance region isdefined as the region interposed between the Bragg reflectors. In thedevice of Example 1, the region denoted by reference numeral 111 is theresonance region.

FIG. 2 shows the resonance region 111, the structure of one period ofthe n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 103 consisting of the n-Al_(0.9)Ga_(0.1)Aslower semiconductor distributed Bragg reflector low refraction layer 103a and the n-Al_(0.15)Ga_(0.85)As lower semiconductor distributed Braggreflector high refraction layer 103 b, and the structure of one periodof the p-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 108 consisting of the p-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer 108a and the p-Al_(0.15)Ga_(0.85)As upper semiconductor distributed Braggreflector high refraction layer 108 b.

In the surface-emitting laser diode of FIG. 1, the n-AlAs selectivelyoxidized layer 104 and the p-AlAs selectively oxidized layer 109 areprovided in the n-Al_(0.9)Ga_(0.1)As lower semiconductor distributedBragg reflector low refraction layer 103 a and the p-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer 108a, respectively, which are in contact with the resonance region, asshown in FIG. 2. Here, the n-AlAs selectively oxidized layer 104 is 30nm thick, and the p-AlAs selectively oxidized layer 109 is 20 nm. On theother hand, the n-Al_(0.9)Ga_(0.1)As lower semiconductor distributedBragg reflector low refraction layer 103 a and the p-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer 108a that are provided with the AlAs selectively oxidized layers 104 and109 each has such a thickness that the phase change of the oscillatinglight in each of the regions including the AlAs layer becomes 3 π/2.

The non-doped Al_(0.15)Ga_(0.85)As resonator spacer layer 105, theGaAs/Al_(0.15)Ga_(0.85)As multi-quantum well active layer 106, thenon-doped Al_(0.15)Ga_(0.85)As resonator spacer layer 107, are adjustedin such a manner that the phase change of the oscillating light in theresonator region to be created becomes equal to 2π, and thus a 1−λ;resonator structure is formed.

To achieve a high stimulated emission rate, theGaAs/Al_(0.15)Ga_(0.85)As multi-quantum well active layer 106 is locatedat an antinode of the standing wave of the oscillating light. On theother hand, to reduce the light diffraction loss, the n-AlAs selectivelyoxidized layer 104 and the p-AlAs selectively oxidized layer 109 areprovided at the joints of the standing wave of the oscillating light. Inthe device shown in FIG. 1, the n-AlAs selectively oxidized layer 104and the AlAs selectively oxidized layer 109 are each situated at thesecond joint counted from the active layer 106, as shown in FIG. 2.

After the crystal growth, a 30 μm square resist pattern is formed in thesurface-emitting laser diode of FIG. 1 by a known photoengravingtechnique. Etching removal is then performed on each layer between thesurface of the p-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As uppersemiconductor distributed Bragg reflector 108 and the middle of then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower distributedsemiconductor Bragg reflector 103 by a known dry etching technique, andthereby a square mesa is formed.

Next, selective oxidation in the direction parallel to the substrate isperformed on the n-AlAs selectively oxidized layer 104 and the p-AlAsselectively oxidized layer 109 by a one-time oxidation process that actsin the direction from the etching end surface to the center of the mesain a heated atmosphere containing steam. By doing so, the selectiveoxide region 112 is formed around the mesa, while the non-oxide regions113 a and 113 b are left at the center.

At this point, the oxidation rates of the n-AlAs selectively oxidizedlayer 104 and the p-AlAs selectively oxidized layer 109 differ with thethicknesses of the respective selective oxide layers 104 and 109. Ingeneral, the relatively thicker n-AlAs selectively oxidized layer 104has a higher oxidation rate. Accordingly, the non-oxide region 113 b isdesigned to have a smaller area than the non-oxide region 113 a. Here,each side of the non-oxide region 113 b is 3 μm long, while each side ofthe non-oxide region 113 a is 10 μm long. Thus, the area of thenon-oxidized (conductive) region 113 b in the electron passage isrelatively smaller than the area of the non-oxidized (conductive) region113 a in the hole passage. The selective oxidation structure thatincludes the relatively small non-oxide region 113 b serves as anoptical mode control structure.

A SiO₂ insulating layer 114 is formed on the entire surface of the waferby a chemical vapor deposition (CVD) technique. After that, spin-coatingwith insulating resin 115 is performed in alignment with the center ofthe mesa, so that the insulating resin on the mesa is removed. The SiO₂insulating layer 114 is then removed from the region from which theinsulating resin has been removed. A 10 μm square resist pattern is nextformed in the light emitting region on the mesa, and deposition iscarried out. The electrode material is removed from the light emittingregion by a lift-off technique, so that a p-side electrode 116 isformed. After the back surface of the n-GaAs substrate 101 is polished,an n-side electrode 117 is formed on the back surface of the substrate101 through a deposition process. Ohmic conduction is then performed onthe electrodes 116 and 117 through annealing.

In the surface-emitting laser diode of FIG. 1, the AlAs selectivelyoxidized layers 109 and 104 are provided in thep-Al_(0.9)Ga_(0.15)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 108 and then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 103, respectively. Each side of thenon-oxidized (conductive) region 113 b formed in then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 103 is 3 μm long, which is shorter than eachside of the non-oxidized (conductive) region 113 a formed in thep-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 108. Here, the refraction of the AlAs oxideis approximately 1.6, and affects the waveguide mode in the resonator.Accordingly, a high-order transverse mode having great electric fieldamplitude in areas other than the center of the mesa has a greatrefraction loss due to the oxide layers, and has the oscillation greatlysuppressed. On the other hand, a fundamental transverse mode havinggreat electric field amplitude at the center of the mesa has a smallrefraction loss due to the oxidation confinement structure, and easilyattains oscillation.

A conventional surface-emitting laser diode has a small non-oxidizedarea in the p-type distributed Bragg reflector, so as to attain steadysingle fundamental transverse-mode oscillation. However, this causeslimitations on outputs of the device due to the decrease of theoscillation area, and an increase of the heat generation from the devicedue to high resistance (roll-over due to the heat).

The device of Example 1, on the other hand, suppresses thetransverse-mode oscillation by virtue of the oxidation confinementstructure provided in the n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)Aslower semiconductor distributed Bragg reflector 103. In this device, then-type distributed Bragg reflector has a lower resistance than thep-type distributed Bragg reflector, and accordingly, the oscillation ofthe high-order transverse mode can be suppressed without an increase inthe resistance of the device.

However, electrons have greater mobility than holes. It is difficult torestrict the carrier injection region effectively to the center of themesa by virtue of the oxidation restricting layer provided in the n-typedistributed Bragg reflector. As a result, the carriers scatter towardthe sides of the mesa, and cause a problem of a decrease of theradiative recombination rate due to the non-radiative recombinationlevels of the sides of the mesa. To avoid this problem, a restrictingstructure should be provided for the holes so as to restrict the regionin which electrons and holes are excited at high density to the centerof the mesa.

To achieve this objective, the device of Example 1 has an oxidationconfinement structure provided in the p-type distributed Bragg reflectorso as to restrict the holes. It is unnecessary to restrict the non-oxideregion to so small as to suppress the oscillation of the high-ordertransverse mode, and the oxidation confinement structure should be onlybig enough to prevent the holes from scattering to the sides of themesa. Accordingly, the oxidation confinement structure can be madelarger so as to obtain high outputs. There is no need to increase thedevice resistance as in the prior art, and adverse influence from theheat output saturation is small. Thus, even greater oscillation can beachieved.

As described above, the device of Example 1 of the present invention canachieve great oscillation in the single fundamental mode, and has ahigher heat output saturation point than conventional devices.

Example 2

FIG. 3 illustrates a surface-emitting laser diode of Example 2 of thepresent invention. The surface-emitting laser diode shown in FIG. 3 is a1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. In the following, thestructure of this surface-emitting laser diode will be described indetail, in conjunction with the production procedures.

In the surface-emitting laser diode of FIG. 3, a crystal growth processis performed in the same manner as the crystal growth process inExample 1. More specifically, the device of FIG. 3 includes: an n-GaAssubstrate 201; an n-GaAs buffer layer 202; a 36-periodn-Al_(0.9)Ga_(0.1)As/GaAs lower semiconductor distributed Braggreflector 203 having each combination of n-Al_(0.9)Ga_(0.1)As/GaAs asone period; a resonance region 211 formed by a non-doped GaAs resonatorspacer 205, a GaInGAs/GaAs multi-quantum well active layer 206, and anon-doped GaAs resonator spacer 207; and a 20-period upper semiconductordistributed Bragg reflector formed by a p-Al_(0.9)Ga_(0.1)As/GaAs uppersemiconductor distributed Bragg reflector 210 and ann-Al_(0.9)Ga_(0.1)As/GaAs upper semiconductor distributed Braggreflector 208. These layers are formed in this order through crystalgrowth, with the substrate 201 being at the bottom. Further, the GaAslayer that is the outermost surface layer of the upper semiconductordistributed Bragg reflector has a p-GaAs contact layer (not shown)formed by high-density carbon that is a p-type dopant in the vicinity ofthe surface.

The upper semiconductor distributed Bragg reflectors 208 and 210 and thelower semiconductor distributed Bragg reflector 203 each has such athickness that the phase change of light in each layer with respect tothe oscillating wavelength becomes π/2, which is the same as in theExample 1. More specifically, each Al_(0.9)Ga_(0.1)As layer is 109.9 nmthick, and each GaAs layer is 95.2 nm thick.

The n-Al_(0.9)Ga_(0.1)As/GaAs lower semiconductor distributed Braggreflector 203 and the p-Al_(0.9)Ga_(0.1)As/GaAs upper semiconductordistributed Bragg reflector 210 include an n-AlAs selectively oxidizedlayer 204 and a p-AlAs selectively oxidized layer 209, respectively.Each of the selectively oxidized layers 204 and 209 is formed by anoxide region 212 that is oxidized through selective oxidation, and anon-oxide region 213 a/213 b that is not oxidized.

FIG. 4 illustrates the surrounding area of the resonance region 211 ofthe surface-emitting laser diode of FIG. 3, in conjunction with thestanding wave of oscillating light.

The structure shown in FIG. 4 includes: the resonance region 211 that isformed by the non-doped GaAs resonator spacer 205, the GaInNAs/GaAsmulti-quantum well active layer 206, and the non-doped GaAs resonatorspacer 207; one period of the n-Al_(0.9)Ga_(0.1)As/GaAs lowersemiconductor distributed Bragg reflector 203 that is formed by ann-Al_(0.9)Ga_(0.1)As lower semiconductor distributed Bragg reflector lowrefraction layer 203 a, the n-AlAs selectively oxidized layer 204, andan n-GaAs lower semiconductor distributed Bragg reflector highrefraction layer 203 b; and a structure that is formed by ap-Al_(0.9)Ga_(0.1)As upper semiconductor distributed Bragg reflector lowrefraction layer 210 a, the p-AlAs selectively oxidized layer 209, ap-GaAs upper semiconductor distributed Bragg reflector high refractionlayer 210 b, a tunnel junction 217, a GaAs upper semiconductordistributed Bragg reflector high refraction layer 208 b, and ann-Al_(0.9)Ga_(0.1)As upper semiconductor distributed Bragg reflector lowrefraction layer 208 a.

In the surface-emitting laser diode of FIG. 3, the n-Al_(0.9)Ga_(0.1)Aslower semiconductor distributed Bragg reflector low refraction layer 203a and the p-Al_(0.9)Ga_(0.1)As upper semiconductor distributed Braggreflector low refraction layer 210 a include the n-AsAl selectivelyoxidized layer 204 and the p-AlAs selectively oxidized layer 209,respectively. Here, the n-AlAs selectively oxidized layer 204 is 30 nmthick, and the p-AlAs selectively oxidized layer 209 is 20 nm thick.

The tunnel junction 217 formed by a p++-GaAs layer and an n++-GaAs layeris interposed between the p-GaAs upper semiconductor distributed Braggreflector high refraction layer 210 b and the n-GaAs upper semiconductordistributed Bragg reflector high refraction layer 208 b.

The n-Al_(0.9)Ga_(0.1)As lower semiconductor distributed Bragg reflectorlow refraction layer 203 a and the p-Al_(0.9)Ga_(0.1)As uppersemiconductor distributed Bragg reflector low refraction layer 210 aeach has such a thickness that the phase change of the oscillating lightin each of the regions including the AlAs selectively oxidized layersbecomes 3π/2, which satisfies the phase conditions of Bragg reflectors.

Likewise, the tunnel junction 217, the p-GaAs upper semiconductordistributed Bragg reflector high refraction layer 210 b, and the n-GaAsupper semiconductor distributed Bragg reflector high refraction layer208 b, each has such a thickness that the phase change of light in eachof the layers becomes 3π/2.

In this device of Example 2, after a mesa is formed in the same manneras in Example 1, a selective oxide region 212 and non-oxide regions 213a and 213 b are formed through selective oxidation, which is also thesame as in Example 1. Here, the areas of the non-oxide regions vary withthe thicknesses of the AlAs selectively oxidized layers. In general, thenon-oxidized (conductive) region 213 a that is to serve as the holepassage has a larger area than the non-oxidized (conductive) region 213b that is to serve as the electron passage. The selective oxidationstructure that includes the non-oxide region 213 b having the smallerarea serves as an optical mode control structure.

An insulating region including a SiO₂ insulating layer 214 andinsulating resin 215 is then formed in the same manner as in Example 1.Further, a p-side electrode 216 a and an n-side electrode 216 b areformed.

Like the device of Example 1, the device of Example 2 has an oxidationconfinement structure provided in the n-Al_(0.9)Ga_(0.1)As/GaAs lowersemiconductor distributed Bragg reflector 203, and thus performstransverse-mode control. Since the resistance of an n-type distributedBragg reflector is lower than the resistance of a p-type distributedBragg reflector, high-order transverse-mode oscillation can besuppressed, without an increase of resistance.

The surface-emitting laser diode of FIG. 3 actually has high outputs,while maintaining single fundamental transverse-mode oscillation. Inthis surface-emitting laser diode, the upper and lower reflectors areformed mainly by n-semiconductor distributed Bragg reflectors that havesmall absorption losses with a p-semiconductor distributed Braggreflector. Thus, a long-wave band surface-emitting laser diode havingexcellent characteristics such as a high slope efficiency and lowoscillation threshold current is realized.

In this manner, a surface-emitting laser diode structure may be providedwith a tunnel junction.

Example 3

FIG. 5 illustrates a surface-emitting laser diode of Example 3 of thepresent invention. The surface-emitting laser diode shown in FIG. 5 is a0.98 μm band surface-emitting laser diode having a GaInAs/GaAsmulti-quantum well structure as an active layer. In the following, thisstructure will be described in detail, in conjunction with theproduction procedures.

In the surface-emitting laser diode of FIG. 5, a crystal growth processis performed in the same manner as the crystal growth process inExample 1. More specifically, the device of FIG. 5 includes: an n-GaAssubstrate 301; an n-GaAs buffer layer 302; a 36-periodn-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Braggreflector 303 having each combination of n-Al_(0.8)Ga_(0.2)As/GaAs asone period; a resonance region 311 formed by a non-doped GaAs resonatorspacer 305, a GaInGAs/GaAs multi-quantum well active layer 306, and anon-doped GaAs resonator spacer 307; and a 20-periodp-Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 308. These layers are formed in this order through crystalgrowth, with the substrate 301 being at the bottom.

Further, the GaAs layer that is the outermost surface layer of the uppersemiconductor distributed Bragg reflector 308 has a p-GaAs contact layer(not shown) formed by high-density carbon that is a p-type dopant in thevicinity of the surface.

The n-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Braggreflector 303 and the p-Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 308 include an n-AlAs selectively oxidizedlayer 304 and a p-AlAs selectively oxidized layer 309, respectively.Each of the selectively oxidized layers 304 and 309 is formed by anoxide region 312 that is oxidized through selective oxidation, and anon-oxide region 313 a/313 b that is not oxidized.

Here, an n-Al_(0.8)Ga_(0.2)As lower semiconductor distributed Braggreflector low refraction layer 303 a, a p-Al_(0.8)Ga_(0.2)As uppersemiconductor distributed Bragg reflector low refraction layer 308 a, ann-GaAs lower semiconductor distributed Bragg reflector high refractionlayer 303 b, and a n-GaAs upper semiconductor distributed Braggreflector high refraction layer 308 b, each has such a thickness thatthe phase change of the oscillating light in each of the semiconductorlayers becomes π/2, which satisfies the phase conditions formulti-reflection of distributed Bragg reflectors. More specifically,each Al_(0.8)Ga_(0.2)As layer is 80.2 nm thick, and each GaAs layer is69.5 nm thick.

Example 3 differs from Example 1 in the location of the p-AlAsselectively oxidized layer 309. In Example 1, the p-AlAs selectivelyoxidized layer 109 is located in the p-Al_(0.9)Ga_(0.1)As uppersemiconductor distributed Bragg reflector low refraction layer 108 a,which is the first layer counted from the resonance region, in thep-Al_(0.9)Ga_(0.1)As/GaAs upper semiconductor distributed Braggreflector 108. In Example 3, on the other hand, the p-AlAs selectivelyoxidized layer 309 is located in the p-Al_(0.8)Ga_(0.2)As uppersemiconductor distributed Bragg reflector low refraction layer 308 a,which is the fifth layer counted from the resonance region.

FIG. 6 illustrates the resonance region 311 and the region surroundingthe p-AlAs selectively oxidized layer 309 in thep-Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 308 of the surface-emitting laser diode of FIG. 5.

FIG. 6 shows the structure of the resonance region 311 interposedbetween one period of the n-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductordistributed Bragg reflector 303 that is formed by then-Al_(0.8)Ga_(0.2)As lower semiconductor distributed Bragg reflector lowrefraction layer 303 a, the n-AlAs selectively oxidized layer 304, andthe n-GaAs lower semiconductor distributed Bragg reflector highrefraction layer 303 b, and one period of the p-Al_(0.8)Ga_(0.2)As/GaAsupper semiconductor distributed Bragg reflector 308 that is formed bythe p-Al_(0.8)Ga_(0.2)As upper semiconductor distributed Bragg reflectorlow refraction layer 308 a, the p-AlAs selectively oxidized layer 309,and the p-GaAs upper semiconductor distributed Bragg reflector highrefraction layer 308 b.

The p-AlAs selectively oxidized layer 309 is located in thep-Al_(0.8)Ga_(0.2)As upper semiconductor distributed Bragg reflector lowrefraction layer 308 a, which is the fifth layer counted from theresonance region 311. The two AlAs selectively oxidized layers. 304 and309 are provided at the locations corresponding to the joints ofoscillating light.

Here, the n-AlAs selectively oxidized layer 304 is 30 nm thick, and thep-AlAs selectively oxidized layer 309 is 20 nm thick. Also, then-Al_(0.8)Ga_(0.2)As lower semiconductor distributed Bragg reflector lowrefraction layer 303 a and the p-Al_(0.8)Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 308 a each has such athickness that the phase change of the oscillating light in this regionincluding the AlAs layers becomes 3π/2.

The resonance region 311 forms a 1-λ resonator structure, which is thesame as in Example 1, and the GaInAs/GaAs multi-quantum well activelayer 306 is located at the antinode of the standing wave of theoscillating light.

In this device of Example 3, after a mesa is formed in the same manneras in Example 1, a selective oxide region 312 and non-oxide regions 313a and 313 b are formed through selective oxidation, which is also thesame as in Example 1. Here, the areas of the non-oxide regions vary withthe thicknesses of the AlAs selectively oxidized layers. In general, thenon-oxidized (conductive) region 313 a that is to serve as the holepassage has a larger area than the non-oxidized (conductive) region 313b that is to serve as the electron passage. The selective oxidationstructure that includes the non-oxide region 313 b having the smallerarea serves as an optical mode control structure.

An insulating region including a SiO₂ insulating layer 314 andinsulating resin 315 is then formed in the same manner as in Example 1.Further, a p-side electrode 316 and an n-side electrode 317 are formed.

The surface-emitting laser diode of FIG. 5 can actually have highoutputs, while maintaining single fundamental transverse-modeoscillation. The location of the optical mode control structure is notlimited to the region surrounding the resonance region. In Example 3,the optical mode control structure can be provided at any location inthe distributed Bragg reflectors.

Example 4

FIG. 7 illustrates a surface-emitting laser diode of Example 4 of thepresent invention. The surface-emitting laser diode shown in FIG. 7 is a0.98 μm band surface-emitting laser diode having a GaInAs/GaAsmulti-quantum well structure as an active layer. In the following, thisstructure will be described in detail, in conjunction with theproduction procedures.

The surface-emitting laser diode of FIG. 7 has the same layer structureas the device of Example 3, except that a p-AlAs selectively oxidizedlayer 409 is located at an antinode of the standing wave of theoscillating light in a p-Al_(0.8)Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 408 a in ap-Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 408. The p-Al_(0.8)Ga_(0.2)As upper semiconductor distributedBragg reflector low refraction layer 408 a is the fifth layer countedfrom a resonance region 411.

FIG. 8 illustrates the surface-emitting laser diode of FIG. 7 in greaterdetail, and the structure shown in FIG. 8 corresponds to the structureshown in FIG. 6 of Example 3. Referring to FIG. 8, the p-AlAsselectively oxidized layer 409 that is 20 nm thick is located at anantinode of the standing wave of the oscillating light in thep-Al_(0.8)Ga_(0.2)As upper semiconductor distributed Bragg reflector lowrefraction layer 408 a in Example 4. The p-Al_(0.8)Ga_(0.2)As uppersemiconductor distributed Bragg reflector low refraction layer 408 a hassuch a thickness that the phase change of the oscillating light in theregion including the p-AlAs selectively oxidized layer 409 and thep-Al_(0.8)Ga_(0.2)As upper semiconductor distributed Bragg reflector lowrefraction layer 408 a becomes 3π/2.

In this device of Example 4, a selective oxide region 412 and non-oxideregions 413 a and 413 b are formed through selective oxidation, which isalso the same as in Example 3. Here, the areas of the non-oxide regionsvary with the thicknesses of the AlAs selectively oxidized layers. Ingeneral, the non-oxidized (conductive) region 413 a that is to serve asthe hole passage has a larger area than the non-oxidized (conductive)region 413 b that is to serve as the electron passage. The selectiveoxidation structure that includes the non-oxide region 413 b having thesmaller area serves as an optical mode control structure. Each side ofthe non-oxidized (conductive) region 413 a is 10 μm long, and each sideof the non-oxidized (conductive) region 413 b is 3 μm long.

Oscillating light of high-order transverse mode has a wider electricfield in the transverse direction, compared with fundamentaltransverse-mode light. Also, the light diffraction loss becomes greaterwhen an oxide layer is located at an antinode of the standing wave ofgreat electric field amplitude. Therefore, a selective oxidationstructure that includes a large non-oxide region is provided at anantinode of the standing wave, so as to minimize the diffraction losswith respect to the fundamental transverse mode and to increase thediffraction loss with respect to the high-order transverse mode. Thus,the surface-emitting laser diode of FIG. 7 can have high outputs, whilemaintaining single fundamental transverse-mode oscillation.

Example 5

FIG. 9 illustrates a surface-emitting laser diode of Example 5 of thepresent invention. The surface-emitting laser diode shown in FIG. 9 is a0.85 μm band surface-emitting laser diode having aGaAs/Al_(0.15)Ga_(0.85)As multi-quantum well structure as an activelayer. This surface-emitting laser diode of FIG. 9 is the same as thedevice of Example 1, except that the conductivity types of the upper andlower structures sandwiching the active layer are reversed. In thefollowing, the device of this example will be described in greaterdetail.

The device of FIG. 9 includes: a p-GaAs substrate 501; a p-GaAs bufferlayer 502; a 36-period p-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lowersemiconductor distributed Bragg reflector 503 having each combination ofp-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As as one period; a resonanceregion 511 that is formed by a non-doped Al_(0.15)Ga_(0.85)As resonatorspacer 505, a GaAs/Al_(0.15)Ga_(0.85)As multi-quantum well active layer506, and a non-doped Al_(0.15)Ga_(0.85)As resonator spacer 507; and a20-period n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 508. These layers are formed in this orderthrough crystal growth, with the substrate 501 being at the bottom. Thep-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 503 and then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 508 include a p-AlAs selectively oxidizedlayer 504 and an n-AlAs selectively oxidized layer 509, respectively.Each of the selectively oxidized layers 504 and 509 is formed by anoxide region 512 that is oxidized through selective oxidation, and anon-oxide region 513 a/513 b that is not oxidized.

FIG. 10 illustrates the region surrounding the resonance region 511 ofthe surface-emitting laser diode of FIG. 9. The structure shown in FIG.10 includes: the resonance region 511; the structure of one period ofthe p-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 503 consisting of a p-Al_(0.9)Ga_(0.1)Aslower semiconductor distributed Bragg reflector low refraction layer 503a, the p-AlAs selectively oxidized layer 504, and ap-Al_(0.15)Ga_(0.85)As lower semiconductor distributed Bragg reflectorhigh refraction layer 503 b; and the structure of one period of then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 508 consisting of an n-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer 508a, the n-AlAs selectively oxidized layer 509, and ann-Al_(0.15)Ga_(0.85)As upper semiconductor distributed Bragg reflectorhigh refraction layer 508 b.

In the surface-emitting laser diode of FIG. 9, the p-AlAs selectivelyoxidized layer 504 and the n-AlAs selectively oxidized layer 509 areprovided in the p-Al_(0.9)Ga_(0.1)As lower semiconductor distributedBragg reflector low refraction layer 503 a and the n-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer 508a, respectively, which are in contact with the resonance region, asshown in FIG. 10. Here, the n-AlAs selectively oxidized layer 509 is 30nm thick, and the p-AlAs selectively oxidized layer 504 is 20 nm. On theother hand, the p-Al_(0.9)Ga_(0.1)As lower semiconductor distributedBragg reflector low refraction layer 503 a and the n-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer 508a that are provided with the AlAs selectively oxidized layers 504 and509 each has such a thickness that the phase change of the oscillatinglight in each of the regions including the AlAs layer becomes 3π/2.

The GaAs/Al_(0.15)Ga_(0.85)As multi-quantum well active layer 506 isprovided at an antinode of the standing wave of the oscillating light,and the p-AlAs selectively oxidized layer 504 and the n-AlAs selectivelyoxidized layer 509 are provided at location corresponding to joints ofthe standing wave. This device also forms a 1−λ; resonator structure.

In the device of Example 5, after a mesa is formed, a selective oxideregion 512 and non-oxidized (conductive) regions 513 a and 513 b areformed through selective oxidation in the same manner as in Example 1.The area of the selective oxide region 512 varies with the differencebetween the thicknesses of the AlAs selectively oxidized layers 504 and509.

In general, the non-oxide region 513 b is designed to have a smallerarea than the non-oxide region 513 a. Here, each side of the non-oxideregion 513 b is 3 μm long, while each side of the non-oxide region 513 ais 10 μm long. The selective oxidation structure that includes thesmaller non-oxide region 513 b serves as an optical mode controlstructure.

An insulating region is then formed with a SiO₂ insulating layer 514 andinsulating resin 515 in the same manner as in Example 1. After that, ap-side electrode 516 and an n-side electrode 517 are formed.

This surface-emitting laser diode of FIG. 9 also can have high outputs,while maintaining single fundamental transverse-mode oscillation.

In this manner, the substrate side can be of p-conductivity type, andthe surface side can be of n-conductivity type, using a p-typesemiconductor substrate.

Example 6

FIG. 11 illustrates a surface-emitting laser diode of Example 6 of thepresent invention. The surface-emitting laser diode shown in FIG. 11 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. This surface-emittinglaser diode also has a so-called intra-cavity contact structure in whichthe electrode for confining carriers is provided on a semiconductorlayer in the device. In the following, this structure will be describedin detail, in conjunction with the production procedures. Thesurface-emitting laser diode of FIG. 11 is formed through crystal growthby a MOCVD method, which is the same as in Example 1, anddimethylhydrazine is employed as the nitride material for the activelayer.

More specifically, the device of FIG. 11 includes an n-GaAs substrate601, an n-GaAs buffer layer 602, a 36-period n-Al_(0.8)Ga_(0.2)As/GaAslower semiconductor distributed Bragg reflector 603 having eachcombination of Al_(0.8)Ga_(0.2)As/GaAs as one period, a resonance region611, and a 20-period non-doped Al_(0.8)Ga_(0.2)As/GaAs uppersemiconductor distributed Bragg reflector 608. These layers are formedin this order through crystal growth, with the substrate 601 being atthe bottom.

The resonance region 611 is formed by a GaInNAs/GaAs multi-quantum wellactive layer 607, a GaAs resonator spacer layer, and a p-AlAsselectively oxidized layer 605.

An n-AlAs selectively oxidized layer 604 is further provided in then-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Braggreflector 603. Each of the selectively oxidized layers 605 and 604 isformed by a selective oxide-region 612 that is oxidized throughselective oxidation, and a non-oxide region 613 a/613 b that is notoxidized.

FIG. 12 illustrates the surrounding area of the resonance region 611 ofthe surface-emitting laser diode of an intra-cavity contact type of FIG.11. More specifically, the structure shown in FIG. 12 includes: theresonance region 611; one period of the n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 603 that is formed by ann-Al_(0.8)Ga_(0.2)As lower semiconductor distributed Bragg reflector lowrefraction layer 609 a, the n-AlAs selectively oxidized layer 604, andan n-GaAs lower semiconductor distributed Bragg reflector highrefraction layer 609 b; and one period of the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector608 that is formed by a non-doped Al₀₈Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 610 a and a non-dopedGaAs upper semiconductor distributed Bragg reflector high refractionlayer 610 b.

As can be seen from FIG. 12, the n-AlAs selectively oxidized layer 604is provided in the n-Al_(0.8)Ga_(0.2)As lower semiconductor distributedBragg reflector low refraction layer 609 a.

The resonance region 611 is formed by a non-doped GaAs resonator spacerlayer 606 a, a GaInNAs/GaAs multi-quantum well structure 607, anon-doped GaAs spacer layer 606 b, a p-GaAs spacer layer 606 c, a p-AlAsselectively oxidized layer 605, a p-GaAs spacer layer 606 d, a p-GaAscontact/resonator spacer layer 606 e, and a non-doped GaAs resonatorspacer layer 606 f. These layers are formed through crystal growth inthis order, with the non-doped GaAs resonator spacer layer 606 a beingclosest to the substrate 601.

The Al_(0.8)Ga_(0.2)As layers 609 a and 610 a that are the lowrefraction layers of the lower semiconductor distributed Bragg reflector603 and the upper semiconductor distributed Bragg reflector 608, and theGaAs layers 609 b and 610 b that are the high refraction layers of thelower semiconductor distributed Bragg reflector 603 and the uppersemiconductor distributed Bragg reflector 608, each has such a thicknessthat the phase change of the oscillating light in each semiconductorlayer becomes π/2, which satisfies the phase conditions formulti-reflection of distributed Bragg reflectors. More specifically,each Al_(0.8)Ga_(0.2)As layer is 108.2 nm thick, and each GaAs layer is95.2 nm thick.

However, as shown in FIG. 12, the n-Al_(0.8)Ga_(0.2)As lowersemiconductor distributed Bragg reflector low refraction layer 609 asandwiching the n-AlAs selectively oxidized layer 604 has such athickness that the phase change of the oscillating light in the n-AlAsselectively oxidized layer 604 and the n-Al_(0.8)Ga_(0.2)As lowersemiconductor distributed Bragg reflector low refraction layer 609 abecomes 3π/2. Here, the n-AlAs selectively oxidized layer 604 is 30 nmthick.

The non-doped GaAs resonator spacer layers 606 a and 606 b, theGaInNAs/GaAs multi-quantum well structure 607, the p-GaAs resonatorspacer layers 606 c and 606 d, the non-doped GaAs resonator spacer layer606 f, the p-AlAs selectively oxidized layer 605, and the p-GaAscontact/resonator spacer layer 606 e, which form the resonance region611, each has such a thickness that the phase change of the oscillatinglight in the resonance region 611 becomes 4 δ, thereby forming a 2−λresonator structure.

Also, the GaInNAs/GaAs multi-quantum well structure 607 is located at anantinode of the standing wave of the oscillating light. On the otherhand, the n-AlAs selectively oxidized layer 604 and the p-AlAsselectively oxidized layer 605 are provided at locations correspondingto joints of the standing wave of the oscillating light, so as to reducethe light diffraction loss. In the device of FIG. 11, the n-AlAsselectively oxidized layer 604 and the p-AlAs selectively oxidized layer605 are located at the second joints, counted from the active layer, ofthe standing wave, as shown in FIG. 12. Here, the p-AlAs selectivelyoxidized, layer 605 is 20 nm thick.

The P-GaAs contact/resonator spacer layer 606 e is located at a joint ofthe standing wave, so as to reduce the light absorption loss caused bythe high-density p-type doped semiconductor layers.

The surface-emitting laser diode of FIG. 11 is fabricated in thefollowing manner. After the crystal growth of each layer, etchingremoval is performed for each layer contained between the surface of thenon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 608 and the surface of the p-GaAs contact/resonator spacerlayer 606 e, by a known photoengraving technique and a known etchingtechnique. A 30 μm square mesa is thus formed as shown in FIG. 12.

A 50 μm square resist pattern is then formed in alignment with thesquare mesa by a photoengraving technique. Etching removal is performedon each layer between the outermost surface and the middle of then-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Braggreflector 603 by a dry etching technique, so that the end surfaces ofthe n-AlAs selectively oxidized layer 604 and the p-AlAs selectivelyoxidized layer 605 are exposed. A double square mesa is thus formed.

In a heated atmosphere containing steam, the oxidation rate iscontrolled by adjusting the thickness difference between the n-AlAsselectively oxidized layer 604 and the p-AlAs selectively oxidized layer605. The non-oxide region 613 a having the larger non-oxidized area andthe 613 b having the smaller non-oxidized area are then formed in themiddle of the mesa, and the selective oxide region 612 is formed in theperipheral area in the mesa.

Here, each side of the non-oxide region 613 b is 5 μm long, and eachside of the non-oxide region 613 a is 10 μm long. In this manner, thearea of the non-oxidized (conductive) region 613 b in the electronpassage is made smaller than the area of the non-oxidized (conductive)region 613 a in the hole passage. Here, the selective oxidationstructure that includes the non-oxide region 613 b having the smallerarea serves as an optical mode control structure.

After a SiO₂ layer 614 is formed on the entire surface of the wafer by achemical vapor deposition (CVD) technique, a 45 μm square resist openingpattern is formed in alignment with the center of the mesa, and the SiO₂at the opening part is removed. A 30 μm resist pattern is next formed onthe p-GaAs contact/resonator spacer layer 606 e in alignment with themesa, and a p-side electrode 615 is formed by a deposition technique ora lift-off technique. The back surface of the substrate 601 is thenpolished, and an n-side electrode 616 is formed on the back surface ofthe substrate 601 by a deposition technique. Ohmic conduction is thencarried out on the electrodes 615 and 616 through annealing.

The surface-emitting laser diode of FIG. 11 can have high outputs, whilemaintaining single fundamental transverse-mode oscillation.

With a p-type semiconductor material, the light absorptivity increasesin long-wave bands including a 1.3 μm band and the like, and theoscillation threshold current also increases due to the absorption lossof high-density p-type doped layers and p-type distributed Braggreflectors. As a result, the slope efficiency tends to decrease.

On the other hand, in the intra-cavity contact structure of Example 6,hole confining is conducted so as to eliminate the need for a p-typedistributed Bragg reflector. The adverse influence from the lightabsorption can be reduced accordingly. A long-wave band surface-emittinglaser diode with a high performance can be thus obtained.

Example 7

FIG. 13 illustrates a surface-emitting laser diode of Example 7 of thepresent invention. This surface-emitting laser diode is a 1.3 μm bandsurface-emitting laser diode having a GaInNAs/GaAs multi-quantum wellstructure as an active layer. The surface-emitting laser diode of FIG.13 also has an intra-cavity contact structure that is provided withelectrodes for carrier confining in the semiconductor layers in thedevice. This device of Example 7 is the same as the device of Example 6,except that the n-AlAs selectively oxidized layer is provided in theresonance region. In the following, this structure will be described indetail, in conjunction with the production procedures.

The surface-emitting laser diode of FIG. 13 includes an n-GaAs substrate701, an n-GaAs buffer layer 702, an n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 703, a resonance region 711,and a non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributedBragg reflector 708. These layers are formed in this order by the samecrystal growth process as in Example 6.

FIG. 14 illustrates the resonance region of the surface-emitting laserdiode of FIG. 13 in greater detail. More specifically, FIG. 14 shows theresonance region 711 interposed between one period of then-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Braggreflector 703 that is formed by an n-Al_(0.8)Ga_(0.2)As lowersemiconductor distributed Bragg reflector low refraction layer 709 a andan n-GaAs lower semiconductor distributed Bragg reflector highrefraction layer 709 b, and one period of the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector708 that is formed by a non-doped Al_(0.8)Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 710 a and a non-dopedGaAs upper semiconductor distributed Bragg reflector high refractionlayer 710 b.

After the formation of the n-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductordistributed Bragg reflector 703 through crystal growth, the resonanceregion 711 and the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 708 are formed through crystal growth. Asshown in FIG. 14, the resonance region 711 includes an n-GaAs resonatorspacer layer 706 a, an n-AlAs selectively oxidized layer 704, an n-GaAsresonator spacer layer 706 b, a non-doped GaAs resonator spacer layer706 c, a GaInNAs/GaAs multi-quantum well structure 707, a non-doped GaAsresonator spacer layer 706 d, a p-GaAs resonator spacer layer 706 e, ap-AlAs selectively oxidized layer 705, a p-GaAs resonator spacer layer706 f, a p-GaAs resonator spacer/contact layer 706 g, and a non-dopedGaAs resonator spacer layer 706 h.

After the crystal growth in the device of FIG. 13, a square mesa isformed by an etching technique, and selective oxidation is performed. ASiO₂ insulating layer 714, a p-side electrode 715, and an n-sideelectrode 716, are then formed. All of these processes are carried outin the same manner as in Example 6.

In this example, the n-AlAs selectively oxidized layer 704 is interposedbetween the n-GaAs resonator spacer layers 706 a and 706 b. Also, then-AlAs selectively oxidized layer 704 and the p-AlAs selectivelyoxidized layer 705 are provided in the resonance region 711, as shown inFIG. 13.

The phase change of oscillating light in the resonance region 711 isequal to 5π. The resonance region 711 thus forms a 2.5−λ resonator. Then-AlAs selectively oxidized layer 704 and the p-AlAs selectivelyoxidized layer 705 have different thicknesses. Each side of thenon-oxide region 713 b provided in the n-type semiconductor layer as theelectron passage is 5 μm long, and each side of the non-oxide region 713a provided in the p-type semiconductor layer as the hole passage is 10μm long. Here, the selective oxidation structure that includes thenon-oxide region 713 b having the smaller area serves as an optical modecontrol structure.

The surface-emitting laser diode of FIG. 13 can also have high outputs,while maintaining single fundamental transverse-mode oscillation.Accordingly, the selectively oxidized layers can be provided in theresonance region.

Example 8

FIG. 15 illustrates a surface-emitting laser diode of Example 8 of thepresent invention. The surface-emitting laser diode shown in FIG. 15 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. This surface-emittinglaser diode also has an intra-cavity contact structure in which theelectrode for confining carriers is provided on a semiconductor layer inthe device. This device of Example 8 has the n-AlAs selectively oxidizedlayer in the resonance region, which is the same as in the device ofExample 7. In this device, the upper reflector is formed by a dielectricmaterial (MgF₂) and a semiconductor material (ZnSe). In the following,this structure will be described in detail, in conjunction with theproduction procedures.

The intra-cavity contact-type surface-emitting laser diode of FIG. 15includes an n-GaAs substrate 801, an n-GaAs buffer layer 802, a36-period n-AlAs/GaAs lower semiconductor distributed Bragg reflector803 having each combination of AlAs/GaAs as one period, a resonanceregion 811, and a p-GaAs contact layer 806 g. These layers are formed inthis order through crystal growth, with the substrate 801 being at thebottom.

FIG. 16 illustrates the region surrounding the resonance region 811 ofthe intra-cavity contact-type surface-emitting laser diode of FIG. 15 ingreater detail. More specifically, FIG. 16 shows one period of then-AlAs/GaAs lower semiconductor distributed Bragg reflector 803 formedby an a-AlAs lower semiconductor distributed Bragg reflector lowrefraction layer 809 a and an n-GaAs lower semiconductor distributedBragg reflector high refraction layer 809 b, and the resonance region811 located on the n-AlAs/GaAs lower semiconductor distributed Braggreflector 803.

In the intra-cavity contact-type surface-emitting laser diode of FIG.15, after the formation of the n-AlAs/GaAs lower semiconductordistributed Bragg reflector 803 through crystal growth, the resonanceregion 811 and the p-GaAs contact layer 806 g are formed also throughcrystal growth. The resonance region 811 is formed by an n-GaAsresonator spacer layer 806 a, an n-AlAs selectively oxidized layer 804,an n-GaAs resonator spacer layer 806 b, a non-doped GaAs resonatorspacer layer 806 c, a GaInNAs/GaAs multi-quantum well structure 807, anon-doped GaAs resonator spacer layer 806 d, a p-GaAs resonator spacerlayer 806 e, a p-Al_(0.95)Ga_(0.5)As selectively oxidized layer 805, anda p-GaAs resonator spacer layer 806 f. The phase change of oscillatinglight in the resonance region 611 is equal to 4δ, and the resonanceregion 811 thus forms a 2−λ resonator structure.

In the intra-cavity contact-type surface-emitting laser diode of FIG.15, after the mesa formation through etching, the selective oxidation,and the formation of a SiO₂ insulating layer 813, the-p-GaAs contactlayer 806 g in the resonance region is removed through etching to reducethe absorption loss, and a 5-period AnSe/MgF₂ upper distributed Braggreflector 808 having each combination of ZnSe/MgF₂ as one period isformed by an electron beam deposition technique. A wet etching techniqueor the like is suitable for the etching of the p-GaAs contact layer 806g. It is preferable to provide a GaInP etching stop layer or the likeunder the p-GaAs contact layer 806 g for better etching control.

After a p-side electrode 815 and an n-side electrode 816 are formed, anetching process is performed on the AnSe/MgF₂ upper distributed Braggreflector 808 by a dry etching technique, so as to form a mesa.

In this example, AlGaAs layers having different Al compositions as AlAsselectively oxidized layers. The p-Al_(0.95)Ga_(0.5)As selectivelyoxidized layer 805 is interposed between the p-GaAs resonator spacerlayers 806 e and 806 f. The n-AlAs selectively oxidized layer 804 isinterposed between the n-GaAs resonator spacer layers 806 a and 806 b.Both the selectively oxidized layers 804 and 805 are 30 nm thick.

In general, an AlGaAs layer containing a larger amount of Al has ahigher oxidation rate. Accordingly, non-oxide regions 813 a and 813 bhaving different areas can be formed through a one-time oxidationprocess by virtue of the difference in the Al compositions. Theoxidation rate can be thus controlled with the difference in the Alcomposition, and the area of the non-oxidized (conductive) region 813 bin the electron passage is smaller than the area of the non-oxidized(conductive) region 813 a in the hole passage. Here, each side of thenon-oxide region 813 b is 5 μm long, while each side of the non-oxideregion 813 a is 10 μm long. The selective oxidation structure thatincludes the smaller non-oxide region 813 b serves as an optical modecontrol structure.

This surface-emitting laser diode of FIG. 15 can perform high-outputoperations, and actually has high outputs, while maintaining singlefundamental transverse-mode oscillation. Also, the device resistanceremains low.

As described above, the upper distributed reflector for asurface-emitting laser diode can be formed by a dielectric material,instead of a semiconductor material.

Example 9

FIG. 17 illustrates a surface-emitting laser diode of Example 9 of thepresent invention. The surface-emitting laser diode shown in FIG. 17 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. This surface-emittinglaser diode has an intra-cavity contact structure in which the electrodefor confining carriers is provided on a semiconductor layer in thedevice. This device of Example 9 has both the p-side and n-sideelectrodes on the surface side of the substrate. In the following, thisstructure will be described in detail, in conjunction with theproduction procedures.

The surface-emitting laser diode of FIG. 17 includes a semi-insulatingGaAs substrate 901, a non-doped GaAs buffer layer 902, a 36-periodnon-doped AlAs/GaAs lower semiconductor distributed Bragg reflector 903having each combination of AlAs/GaAs as one period, a resonance region911, and a 20-period non-doped Al_(0.8)Ga_(0.2)As/GaAs uppersemiconductor distributed Bragg reflector 908 having each combination ofAl_(0.8)Ga_(0.2)As/GaAs as one period. These layers are formed in thisorder through crystal growth, with the substrate 901 being at thebottom.

FIG. 18 illustrates the region surrounding the resonance region 911 ofthe surface-emitting laser diode of FIG. 17 in greater detail. Morespecifically, FIG. 18 shows one period of the non-doped AlAs/GaAs lowersemiconductor distributed Bragg reflector 903 formed by a non-doped AlAslower semiconductor distributed Bragg reflector low refraction layer 909a and a non-doped GaAs lower semiconductor distributed Bragg reflectorhigh refraction layer 909 b, the resonance region 911 located above thenon-doped AlAs/GaAs lower semiconductor distributed Bragg reflector 903,and one period of the non-doped Al_(0.8)Ga_(0.2)As/GaAs uppersemiconductor distributed Bragg reflector 908 formed by a non-dopedAl_(0.8)Ga_(0.2)As upper semiconductor distributed Bragg reflector lowrefraction layer 910 a and a non-doped GaAs upper semiconductordistributed Bragg reflector high refraction layer 910 b.

In the intra-cavity contact-type surface-emitting laser diode of FIG.17, after the formation of the non-doped AlAs/GaAs lower semiconductordistributed Bragg reflector 903 through crystal growth, the resonanceregion 911 and the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 908 are formed also through crystal growth,as shown in FIG. 18. The resonance region 911 is formed by an n-GaAscontact/resonator spacer layer 906 a, an n-GaAs resonator spacer layer906 b, an n-AlAs selectively oxidized layer 904, an n-GaAs resonatorspacer layer 906 c, a non-doped GaAs resonator spacer layer 906 d, aGaInNAs/GaAs multi-quantum well structure 907, a non-doped GaAsresonator spacer layer 906 e, a p-GaAs resonator spacer layer 906 f, ap-Al_(0.98)Ga_(0.02)As selectively oxidized layer 905, and a p-GaAsresonator spacer layer 906 g, a p-GaAs contact/resonator spacer layer906 h, and a non-doped GaAs resonator spacer layer 906 i.

In this device of Example 9, the p-GaAs contact/resonator spacer layer906 h for gaining conduction with the p-side electrode, and the n-GaAscontact/resonator spacer layer 906 a for gaining conduction with then-side electrode, are employed as shown in FIG. 17. Etching is performedon the device of FIG. 17 so as to expose the surfaces of the contactlayers 906 h and 906 a. A double square mesa is thus formed. After that,a selective oxide region 912 and non-oxidized (conductive) regions 913 aand 913 b are formed in a heated atmosphere containing steam. An n-sideelectrode 915 and a p-side electrode 914 are then formed.

In this example, the areas of the non-oxide regions are controlled withthe Al composition difference between the selectively oxidized layers.More specifically, the p-Al_(0.98)Ga_(0.02)As selectively oxidized layer905 is provided in the hole passage, and the n-AsAl selectively oxidizedlayer 904 is provided in the electron passage, so that the area of thenon-oxidized (conductive) region 913 b in the electron passage becomessmaller than the area of the non-oxidized (conductive) region 913 a inthe hole passage.

Here, each side of the non-oxide region 913 b provided in the n-typesemiconductor layer that serves as the electron passage is 3 μm long,while each side of the non-oxide region 913 a provided in the p-typesemiconductor layer that serves as the hole passage is 10 μm long. Theselective oxidation structure that includes the smaller non-oxide region913 b serves as an optical mode control structure.

This surface-emitting laser diode of FIG. 17 can perform high-outputoperations, and actually has high outputs, while maintaining singlefundamental transverse-mode oscillation. Also, the device resistanceremains low.

This device of Example 9 has both the p-side and n-side electrodes onthe contact layers provided in the resonator region, and accordingly,has a structure that does not guide carriers via the semiconductordistributed Bragg reflectors. With this structure, it is not necessaryto perform impurity doping on the semiconductor distributed Braggreflectors, and the light absorption loss caused by free carrierabsorption and the like can be reduced. Thus, a long-wave bandintra-cavity contact-type surface-emitting laser diode with an excellentperformance can be obtained.

Example 10

FIG. 19 illustrates a surface-emitting laser diode of Example 10 of thepresent invention. The surface-emitting laser diode shown in FIG. 19 isa 670-nm band visible surface-emitting laser diode having aGaInP/AlGaInP multi-quantum well structure as an active layer. Thissurface-emitting laser diode has an intra-cavity contact structure inwhich the electrode for confining carriers is provided on asemiconductor layer in the device. This device of Example 10 also hasboth the p-side and n-side electrodes on the outer surface, but has adifferent structure from the device of Example 9. In the following, thisstructure will be described in detail, in conjunction with theproduction procedures.

The surface-emitting laser diode of FIG. 19 is fabricated by a MOCVDtechnique, using phosphine (PH₃) as a phosphorus (p) material anddimethylzinc (DMZn) as a p-type dopant for part of the layers.

The surface-emitting laser diode of FIG. 19 includes a semi-insulatingGaAs substrate 1001, a non-doped GaAs buffer layer 1002, a 56-periodnon-doped Al_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As lower semiconductordistributed Bragg reflector 1003 having each combination ofAl_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As as one period, a resonance region1011, and a p-(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P contact layer 1006 h.These layers are formed in this order through crystal growth, with thesubstrate 1001 being at the bottom.

FIG. 20 illustrates the region surrounding the resonance region 1011 ofthe surface-emitting laser diode of FIG. 19 in greater detail. Morespecifically, FIG. 20 shows one period of the non-dopedAl_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As lower semiconductor distributedBragg reflector 1003 formed by a non-doped Al_(0.9)Ga_(0.1)As lowersemiconductor distributed Bragg reflector low refraction layer 1009 aand a non-doped Al_(0.5)Ga_(0.5)As lower semiconductor distributed Braggreflector high refraction layer 1009 b, the resonance region 1011located above the non-doped Al_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As lowersemiconductor distributed Bragg reflector 1003, and the p-GaAs contactlayer 1006 h.

As shown in FIG. 20, a non-doped AlAs selectively oxidized layer 1004 isprovided at a location corresponding to a joint of the standing wave ofthe oscillating light in the non-doped Al_(0.9)Ga_(0.1)As lowersemiconductor distributed Bragg reflector low refraction layer 1009 a,which is closest to the active layer side of the non-dopedAl_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As lower semiconductor distributedBragg reflector 1003.

In the surface-emitting laser diode of FIG. 19, after the formation ofthe non-doped Al_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As lower semiconductordistributed Bragg reflector 1003 through crystal growth, further crystalgrowth is carried out to form an n-(Al₀₅Ga_(0.5))_(0.5)In_(0.5)Pcontact/resonator spacer layer 1006 a, ann-(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P resonator spacer layer 1006 b, anon-doped (Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P resonator spacer layer 1006c, a non-doped (Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P resonator spacer layer1006 d, a GaInP/(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P multi-quantum wellstructure 1007, a non-doped (Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P resonatorspacer layer 1006 e, a p-(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P resonatorspacer layer 1006 f, a p-Al_(0.98)Ga_(0.02)As selectively oxidized layer1005, and a p-(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P resonator spacer layer1006 g, and the p-GaAs contact layer 1006 h, as shown in FIG. 20.

Here, the p-Al_(0.98)Ga_(0.02)As selectively oxidized layer 1005 isprovided at a location corresponding to a joint of the standing wave ofoscillating light, and has a different thickness and Al composition fromthe non-doped AlAs selectively oxidized layer 1004. More specifically,the p-Al_(0.98)Ga_(0.02)As selectively oxidized layer 1005 is 20 nmthick, and the non-doped AlAs selectively oxidized layer 1004 is 30 nmthick. The resonance region 1011 forms a 2.5−λ resonator structure.

A double square mesa structure shown in FIG. 19 is then formed by aknown photoengraving technique and a known dry etching technique. Toreduce the oscillating light absorption, etching removal is performed onthe p-GaAs contact layer 1006 h in the resonance region 1011.

Oxidation is then performed on the etching end surfaces of thep-Al_(0.98)Ga_(0.02)As selectively oxidized layer 1005 and the non-dopedAlAs selectively oxidized layer 1004 in a heated atmosphere containingsteam, so as to form a selective oxide region 1012 and non-oxide regions1013 a and 1013 b. The oxidation rate of the selectively oxidized layersare controlled by adjusting the Al composition and layer thicknesses. Inthis device, the Al composition and thicknesses of the selectivelyoxidized layers are adjusted so that each side of the non-oxide region1013 a becomes 10 μm long, and that each side of the non-oxide region1013 b becomes 3 μm long. Here, the selective oxidation structure thatincludes the smaller non-oxide region 1013 b serves as an optical modecontrol structure.

A 7-period TiO₂/SiO₂ upper dielectric distributed Bragg reflector 1008having each combination of TiO₂/SiO₂ as one period is formed by anelectron beam deposition technique, and is shaped into the mesa shown inFIG. 19 by a known dry etching technique. After that, a p-side electrode1014 and an n-side electrode 1015 are formed.

In the surface-emitting laser diode of FIG. 19, the two electrodes 1014and 1015 provided on the surface of the substrate guide the carriers,and the oxide insulating layers formed in the non-dopedAl_(0.9)Ga_(0.1)As/Al_(0.5)Ga_(0.5)As lower semiconductor distributedBragg reflector 1003 does not adversely affect the electric resistance.

This device of Example 10 has both the p-side and n-side electrodes onthe contact layers provided in the resonator region, and accordingly,has a structure that does not guide carriers via the semiconductordistributed Bragg reflectors. With this structure, it is not necessaryto perform impurity doping on the semiconductor distributed Braggreflectors, and the light absorption loss caused by free carrierabsorption and the like can be reduced. As the upper distributed Braggreflector is made of a dielectric material, the absorption loss can befurther reduced. In a visible band in which single fundamentaltransverse-mode control is performed, it is necessary to reduce thenon-oxidized area that easily increases the resistance and is readilyinfluenced by heat generation. However, the device of Example 10 has thesmaller non-oxide region 1013 b outside the current passage, so thatincreases of resistance due to the non-oxide region 1013 b can beprevented.

This surface-emitting laser diode of FIG. 19 can perform high-outputoperations, and actually has high outputs, while maintaining singlefundamental transverse-mode oscillation. Also, the device resistanceremains very low.

Example 11

FIG. 21 illustrates a surface-emitting laser diode of Example 11 of thepresent invention. The surface-emitting laser diode shown in FIG. 21 isa 1.3 μm band surface-emitting laser diode having a GaInNAsSb/GaAsmulti-quantum well structure as an active layer. This surface-emittinglaser diode has an intra-cavity contact structure in which the electrodefor confining carriers is provided on a semiconductor layer in thedevice. This device of Example 11 also has a selective oxidationstructure that performs oscillation transverse-mode control in a regionoutside the carrier conduction region. In the following, this structurewill be described in detail.

The structure of a resonance region 1111 of the surface-emitting laserdiode of FIG. 21 is similar to the resonance region of the device ofExample 6. The surface-emitting laser diode of Example 11 has aselective oxidation structure formed by a non-doped AlAs selectivelyoxidized layer in a non-doped upper distributed Bragg reflector, insteadof the selective oxidation structure formed by the n-AlAs selectivelyoxidized layer 604 provided in the n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 603 in Example 6. Thesurface-emitting laser diode of Example 11 further has a GaInNAsSb/GaAsmulti-quantum well structure as an active layer.

The device of FIG. 21 includes an n-GaAs substrate 1101, ann-GaAs-buffer layer 1102, an n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 1103, the resonance region1111, and a non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 1108. These layers are formed in this orderthrough crystal growth, with the substrate 1101 being at the bottom.

FIG. 22 illustrates the region surrounding the resonance region 1111 ofthe surface-emitting laser diode of FIG. 21 in greater detail. Morespecifically, FIG. 22 shows one period of the n-Al_(0.8)Ga_(0.2)As/GaAslower semiconductor distributed Bragg reflector 1103 formed by ann-Al_(0.8)Ga_(0.2)As lower semiconductor distributed Bragg reflector lowrefraction layer 1109 a and an n-GaAs lower semiconductor distributedBragg reflector high refraction layer 1109 b, one period of thenon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 1108 formed by a non-doped Al_(0.8)Ga_(0.2)As uppersemiconductor distributed Bragg reflector low refraction layer 1110 aand a non-doped GaAs upper semiconductor distributed Bragg reflectorhigh refraction layer 1110 b, and the resonance region 1111 interposedbetween the one period of the n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 1103 and the one period of thenon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 1108.

After the formation of the n-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductordistributed Bragg reflector 1103 through crystal growth, further crystalgrowth is carried out to form the resonance region 1111 that includes anon-doped GaAs resonator spacer layer 1106 a, a GaInNAsSb/GaAsmulti-quantum well structure 1107, a non-doped GaAs spacer layer 1106 b,a p-GaAs spacer layer 1106 c, a p-AlAs selectively oxidized layer 1105,a p-GaAs spacer layer 1106 d, a p-GaAs contact/resonator spacer layer1106 e, and a non-doped GaAs spacer layer 1106 f.

A non-doped AlAs selectively oxidized layer 1104 is further provided inthe non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributedBragg reflector 1108. The p-AlAs selectively oxidized layer 1105 isthinner than the non-doped AlAs selectively oxidized layer 1104.

In the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributedBragg reflector 1108, the non-doped AlAs selectively oxidized layer 1104is provided in the non-doped Al_(0.8)Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 1110 a, which islocated at the first joint, counted from the side of the resonanceregion 1111, of the standing wave of the oscillating light. Thenon-doped Al_(0.8)Ga_(0.2)As upper semiconductor distributed Braggreflector low refraction layer 1110 a that contains the non-doped AlAsselectively oxidized layer 1104 has such a thickness that the phasechange of the light in the non-doped AlAs selectively oxidized layer1104 and the non-doped Al_(0.8)Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 1110 a becomes 3π/2.Likewise, the p-AlAs selectively oxidized layer 1105 is provided at alocation corresponding to a joint of the standing wave of oscillatinglight.

After the formation of a double square mesa, selective oxidation isperformed on the two selectively oxidized layers 1104 and 1105 in aheated atmosphere containing steam, so as to form a selective oxideregion 1112 and non-oxide regions 1113 a and 1113 b. The oxidation rateof the selectively oxidized layers is controlled by adjusting the layerthicknesses. Each side of the non-oxide region 1113 b in the non-dopedAlAs selectively oxidized layer 1104 is 5 μm long, while each side ofthe non-oxide region 1113 a in the p-AlAs selectively oxidized layer1105 that serves as the hole passage is 10 μm long. Here, the selectiveoxidation structure that includes the smaller non-oxide region 1113 bserves as an optical mode control structure.

A SiO₂ insulating layer 1114, a p-side electrode 1115, and an n-sideelectrode 1116, are then formed to thereby complete the surface-emittinglaser diode of FIG. 21.

The surface-emitting laser diode of FIG. 21 does not guide current viathe upper semiconductor distributed Bragg reflector 1108. As the uppersemiconductor distributed Bragg reflector 1108 is non-doped and a p-typedistributed Bragg reflector is not employed in this structure, theabsorption loss is small. Furthermore, the non-oxide region 1113 bprovided in the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 1108 does not adversely affect theresistance. Thus, the device resistance constantly remains very low.

This surface-emitting laser diode of FIG. 21 can perform high-outputoperations, and actually has high outputs, while maintaining singlefundamental transverse-mode oscillation.

As described above, a long-wave band intra-cavity contact-typesurface-emitting laser diode with an excellent performance can beobtained.

Example 12

FIG. 23 illustrates a surface-emitting laser diode of Example 12 of thepresent invention. The surface-emitting laser diode shown in FIG. 23 isa 1.3 μm band surface-emitting laser diode having a GaInNAsSb/GaAsmulti-quantum well structure as an active layer. This surface-emittinglaser diode has an intra-cavity contact structure in which the electrodefor confining carriers is provided on a semiconductor layer in thedevice. This device of Example 12 differs from the device of Example 11in that the p-side and n-side electrodes are both provided on the outersurface of the device. In the following, this structure will bedescribed in detail.

The device of FIG. 23 includes a semi-insulating GaAs substrate 1201, anon-doped GaAs buffer layer 1202, a non-doped AlAs/GaAs lowersemiconductor distributed Bragg reflector 1203, a resonance region 1211,and a non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributedBragg reflector 1208. These layers are formed in this order throughcrystal growth, with the substrate 1201 being at the bottom.

FIG. 24 illustrates the region surrounding the resonance region 1211 ofthe surface-emitting laser diode of FIG. 23 in greater detail. Morespecifically, FIG. 24 shows one period of the non-doped AlAs/GaAs lowersemiconductor distributed Bragg reflector 1203 formed by a non-dopedAlAs lower semiconductor distributed Bragg reflector low refractionlayer 1209 a and a non-doped GaAs lower semiconductor distributed Braggreflector high refraction layer 1209 b, the resonance region 1211provided above the one period of the non-doped AlAs/GaAs lowersemiconductor distributed Bragg reflector 1203, and one period of thenon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 1208 formed by a non-doped Al_(0.8)Ga_(0.2)As uppersemiconductor distributed Bragg reflector low refraction layer 1210 aand a non-doped GaAs upper semiconductor distributed Bragg reflectorhigh refraction layer 1210 b.

In the intra-cavity contact-type surface-emitting laser diode of FIG.23, after the formation of the non-doped AlAs/GaAs lower semiconductordistributed Bragg reflector 1203 through crystal growth, further crystalgrowth is carried out to form the resonance region 1211 and thenon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 1208. As shown in FIG. 24, the resonance region 1211 includesa non-doped GaAs resonator spacer layer 1206 a, an n-GaAscontact/resonator spacer layer 1206 b, an n-AlAs selectively oxidizedlayer 1204, an n-GaAs resonator spacer layer 1206 c, a non-doped GaAsresonator spacer layer 1206 d, a GaInNAsSb/GaAs multi-quantum wellstructure 1207, a non-doped GaAs resonator spacer layer 1206 e, a p-GaAsresonator spacer layer 1206 f, a p-AlAs selectively oxidized layer 1205,a p-GaAs resonator spacer layer 1206 g, a p-GaAs contact/resonatorspacer layer 1206 h, and a non-doped GaAs resonator spacer layer 1206 i.In this example, to reduce the absorption loss due to free carriers, then-GaAs contact/resonator spacer layer 1206 b is also provided at thelocation of the standing wave of oscillating light.

In the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributedBragg reflector 1208, the non-doped AlAs selectively oxidized layer 1204and the p-AlAs selectively oxidized layer 1205 are provided at locationscorresponding to joints of the standing wave of the oscillating light inthe resonance region 1211, as shown in FIG. 24. The non-doped AlAsselectively oxidized layer 1204 is thicker than the p-AlAs selectivelyoxidized layer 1205.

After the crystal growth of the above layers, a double square mesa isformed by a known photoengraving technique and a dry etching technique.Selective oxidation is then performed to form a selective oxide region1212 and non-oxide regions 1213 a and 1213 b. Here, the sizes of thenon-oxide regions 1213 a and 1213 b are controlled by adjusting thethicknesses of the AlAs selectively oxidized layers 1204 and 1205. Thenon-oxide region 1213 a has a larger area than the non-oxide region 1213b. The selective oxidation structure that includes the smaller non-oxideregion 1213 b serves as an optical mode control structure.

A p-side electrode 1214 and an n-side electrode 1215 are then formed tothereby complete the surface-emitting laser diode of FIG. 23.

The intra-cavity contact-type surface-emitting laser diode of FIG. 23does not guide current via the upper semiconductor distributed Braggreflector 1208. The non-oxide region 1213 b provided in the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector1208 does not adversely affect the resistance. Thus, the deviceresistance constantly remains very low. Also, with the non-oxide region1213 b provided in the non-doped Al_(0.8)Ga_(0.2)As/GaAs uppersemiconductor distributed Bragg reflector 1208, transverse-mode controlcan be performed, and single fundamental transverse-mode oscillation canbe achieved with high outputs.

This surface-emitting laser diode of FIG. 23 can thus performhigh-output operations, and actually has high outputs, while maintainingsingle fundamental transverse-mode oscillation.

In this device of Example 12, the upper and lower semiconductordistributed Bragg reflectors are both non-doped, and accordingly, thelight absorption loss is minimized. Thus, a long-wave band intra-cavitycontact-type surface-emitting laser diode with an excellent performancecan be obtained.

Example 13

FIG. 25 illustrates a surface-emitting laser diode of Example 13 of thepresent invention. The surface-emitting laser diode shown in FIG. 25 isa 0.85 μm band surface-emitting laser diode having aGaAs/Al_(0.15)Ga_(0.85)As multi-quantum well structure as an activelayer. This device of Example 13 has two or more selective oxidationstructures each having a small-area non-oxidized (conductive) regionthat is provided in the n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lowersemiconductor distributed Bragg reflector in the device of Example 1. Inthe following, this structure will be described in detail.

The device of FIG. 25 has the same layer structure as the device ofExample 1, except for the number of n-AlAs selectively oxidized layers1304 provided in an n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lowersemiconductor distributed Bragg reflector 1303. The layers in the layerstructure of this example are also formed through crystal growth. Thedevice of FIG. 25 has three n-AlAs selectively oxidized layers 1304.

FIG. 26 illustrates the region surrounding the resonance region of thesurface-emitting laser diode of FIG. 25 in greater detail. Morespecifically, FIG. 26 shows three periods of then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 1303 each formed by an n-Al_(0.9)Ga_(0.1)Aslower semiconductor distributed Bragg reflector low refraction layer1303 a and an n-Al_(0.15)Ga_(0.85)As lower semiconductor distributedBragg reflector high refraction layer 1303 b, a resonance region 1311provided above the three periods of then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 1303, and one period of ap-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 1308 formed by a p-Al_(0.9)Ga_(0.1)As uppersemiconductor distributed Bragg reflector low refraction layer 1308 aand a p-Al_(0.15)Ga_(0.85)As upper semiconductor distributed Braggreflector high refraction layer 1308 b;

-   -   In the surface-emitting laser diode of FIG. 25, one n-AlAs        selectively oxidized layer 1304 is formed in each        n-Al_(0.9)Ga_(0.1)As lower semiconductor distributed Bragg        reflector low refraction layer 1303 a, starting from the one        closest to the resonance region 1311, as shown in FIG. 26. There        are three n-AlAs selectively oxidized layers 1304 in total. Each        of the n-AlAs selectively oxidized layers 1304 is located at a        joint of the standing wave of oscillating light, and is thicker        than a p-AlAs selectively oxidized layer 1309.

In the device of FIG. 25, after the crystal growth of the above layers,a mesa is formed, and selective oxidation is performed to form aselective oxide region 1312 and non-oxide regions 1313 a and 1313 b. Aseach of the n-AlAs selectively oxidized layers 1304 is thicker than thep-AlAs selectively oxidized layer 1309, the non-oxide region 1313 a hasa larger area than each non-oxide region 1313 b. Here, the selectiveoxidation structures that include the non-oxide regions 1313 b serve ashigh-order transverse-mode suppressing layers.

After the above selective oxidation, a SiO₂ insulating layer 1314,insulating resin 1315, a p-side electrode 1316, and an n-side electrode1317 are formed to thereby complete the surface-emitting laser diode ofFIG. 25.

This surface-emitting laser diode of FIG. 25 can perform high-outputoperations, and actually has high outputs, while maintaining singlefundamental transverse-mode oscillation. The surface-emitting laserdiode of FIG. 25 has two or more (three) selective oxidation structureseach including a non-oxide region 1313 b in then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector. With this structure, the transverse-modeselecting capacity is increased, and single fundamental transverse-modeoscillation can be achieved with high outputs.

As described above, a long-wave band surface-emitting laser diode withan excellent performance can be obtained.

Example 14

FIG. 27 illustrates a surface-emitting laser diode of Example 14 of thepresent invention. The surface-emitting laser diode shown in FIG. 27 isa 0.85 μm band surface-emitting laser diode having aGaAs/Al_(0.15)Ga_(0.85)As multi-quantum well structure as an activelayer. This device of Example 14 has the same layer structure as thedevice of Example 5, except that there are two or more selectiveoxidation structures each including a non-oxidized (conductive) regionhaving a small area in the n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)Asupper semiconductor distributed Bragg reflector. This device of Example14 also has the same structure as the device of Example 13, except thatthe conductivity types of the upper and lower layer structuressandwiching the active layer are reversed. In the following, thestructure of this device will be described in detail.

The device of FIG. 27 has the same layer structure as the device ofExample 5, except for the number of n-AlAs selectively oxidized layers1409 provided in an n-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As uppersemiconductor distributed Bragg reflector 1408. The layers in the layerstructure of this example are also formed through crystal growth. Thedevice of FIG. 25 has three n-AlAs selectively oxidized layers 1409.

FIG. 28 illustrates the region surrounding the resonance region 1411 ofthe surface-emitting laser diode of FIG. 27 in greater detail. Morespecifically, FIG. 28 shows one period of ap-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 1403 formed by a p-Al_(0.9)Ga_(0.1)As lowersemiconductor distributed Bragg reflector low refraction layer 1403 aand a p-Al_(0.15)Ga_(0.85)As lower semiconductor distributed Braggreflector high refraction layer 1403 b, the resonance region 1411provided above the one period of thep-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lower semiconductordistributed Bragg reflector 1403, and three periods of then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 1408 each formed by an n-Al_(0.9)Ga_(0.1)Asupper semiconductor distributed Bragg reflector low refraction layer1408 a and an n-Al_(0.15)Ga_(0.85)As upper semiconductor distributedBragg reflector high refraction layer 1408 b.

In the surface-emitting laser diode of FIG. 27, one n-AlAs selectivelyoxidized layer 1409 is formed in each n-Al_(0.9)Ga_(0.1)As uppersemiconductor distributed Bragg reflector low refraction layer 1408 a,starting from the one closest to the resonance region 1411, as shown inFIG. 28. There are three n-AlAs selectively oxidized layers 1409 intotal. Each of the n-AlAs selectively oxidized layers 1409 is located ata joint of the standing wave of oscillating light, as shown in FIG. 28,and is thicker than a p-AlAs selectively oxidized layer 1404.

In the device of FIG. 27, after the crystal growth of the above layers,a mesa is formed, and selective oxidation is performed to form aselective oxide region 1412 and non-oxide regions 1413 a and 1413 b. Aseach of the n-AlAs selectively oxidized layers 1409 is thicker than thep-AlAs selectively oxidized layer 1404, each non-oxide region 1413 b hasa smaller area than the non-oxide region 1413 a. Here, the selectiveoxidation structures that include the non-oxide regions 1413 b serve ashigh-order transverse-mode suppressing layers.

After the above selective oxidation, a SiO₂ insulating layer 1414,insulating resin 1415, a p-side electrode 1417, and an n-side electrode1416 are formed to thereby complete the surface-emitting laser diode ofFIG. 27.

This surface-emitting laser diode of FIG. 27 can perform high-outputoperations, and actually has high outputs, while maintaining singlefundamental transverse-mode oscillation. The surface-emitting laserdiode of FIG. 27 has two or more (three) selective oxidation structureseach including a non-oxide region 1413 b in then-Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector. With this structure, the transverse-modeselecting capacity is increased, and single fundamental transverse-modeoscillation can be achieved with high outputs.

As described above, a long-wave band surface-emitting laser diode withan excellent performance can be obtained.

Example 15

FIG. 29 illustrates a surface-emitting laser diode of Example 15 of thepresent invention. The surface-emitting laser diode shown in FIG. 29 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. This device of Example15 has the same structure as the device of Example 11, except that thereare two or more selective oxidation structures each including anon-oxide region having a small area in the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector.In the following, this structure will be described in detail.

The device of FIG. 29 has the same layer structure as the device ofExample 11, except for the number of n-AlAs selectively oxidized layers1504 provided in a non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 1508. The layers in the layer structure ofthis example are also formed through crystal growth. The device of FIG.29 has four n-AlAs selectively oxidized layers 1504.

FIG. 30 illustrates the region surrounding the resonance region 1511 ofthe surface-emitting laser diode of FIG. 29 in greater detail. Morespecifically, FIG. 30 shows the resonance region 1511, one period of ann-AlAs/GaAs lower semiconductor distributed Bragg reflector 1503 formedby an n-AlAs lower semiconductor distributed Bragg reflector lowrefraction layer 1509 a and an n-GaAs lower semiconductor distributedBragg reflector high refraction layer 1509 b, and five periods of thenon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 1508 each formed by a non-doped Al_(0.8)Ga_(0.2)As uppersemiconductor distributed Bragg reflector low refraction layer 1510 aand a non-doped GaAs upper semiconductor distributed Bragg reflectorhigh refraction layer 1510 b.

In the device of FIG. 29, after the formation of the n-AlAs/GaAs lowersemiconductor distributed Bragg reflector 1503 through crystal growth,further crystal growth is carried out to form the resonance region 1511and the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 1508 in the same manner as in Example 11.The resonance region 1511 includes a non-doped GaAs resonator spacerlayer 1506 a, a GaInNAs/GaAs multi-quantum well structure 1507, anon-doped GaAs spacer layer 1506 b, a p-GaAs spacer layer 1506 c, ap-AlAs selectively oxidized layer 1505, a p-GaAs spacer layer 1506 d, ap-GaAs contact/resonator spacer layer 1506 e, and a non-doped GaAsspacer layer 1506 f.

In the surface-emitting laser diode of FIG. 29, one non-doped AlAsselectively oxidized layer 1504 is formed in each non-dopedAl_(0.8)Ga_(0.2)As upper semiconductor distributed Bragg reflector lowrefraction layer 1510 a, starting from the one closest to the resonanceregion 1511, as shown in FIG. 30. There are four non-doped AlAsselectively oxidized layers 1504 in total. Each of the non-doped AlAsselectively oxidized layers 1504 is located at a joint of the standingwave of oscillating light, as shown in FIG. 30, and is thicker than thep-AlAs selectively oxidized layer 1505.

In the device of FIG. 29, after the crystal growth of the above layers,a double mesa is formed, and selective oxidation is performed to form aselective oxide region 1512 and non-oxide regions 1513 a and 1513 b.Each side of each non-oxide region 1513 b is 5 μm long, and each side ofthe non-oxide region 1513 a is 10 μm long. Here, the selective oxidationstructures that include the non-oxide regions 1513 b serve as high-ordertransverse-mode suppressing layers.

The surface-emitting laser diode of FIG. 29 has the two or more (four)non-doped AlAs selectively oxidized layers 1504 in the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector1508, and employs the two or more (four) non-oxide regions 1513 b. Withthis structure, the transverse-mode selecting capacity is increased, andsingle fundamental transverse-mode oscillation can be achieved with highoutputs. Furthermore, the device resistance is very low, because thenon-oxide regions 1513 a each having a small area are located outsidethe current passage.

As described above, a long-wave band surface-emitting laser diode withan excellent performance can be obtained.

Example 16

FIG. 31 illustrates a surface-emitting laser diode of Example 16 of thepresent invention. The surface-emitting laser diode shown in FIG. 31 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. This device of Example16 has the same structure as the device of Example 6, except that thereare two or more selective oxidation structures each including anon-oxide region having a small area in the n-Al_(0.8)Ga_(0.2)As/GaAslower semiconductor distributed Bragg reflector. In the following, thisstructure will be described in detail.

The device of FIG. 31 has the same layer structure as the device ofExample 6, except for the number of n-AlAs selectively oxidized layers1604 provided in an n-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductordistributed Bragg reflector 1603. The layers in the layer structure ofthis example are also formed through crystal growth. The layer structureof a resonance region 1611 is exactly the same as the resonance region611 of Example 6, and therefore explanation of the layer structure isomitted in this description. The device of FIG. 31 has three n-AlAsselectively oxidized layers 1604.

The surface-emitting laser diode of FIG. 31 includes an n-GaAs substrate1601, an n-GaAs buffer layer 1602, the n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 1603, the resonance region1611, and a non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 1608. These layers are formed throughcrystal growth in this order, with the n-GaAs substrate 1601 being atthe bottom.

The resonance region 611 is formed by a GaAs resonator spacer layer1606, a GaInNAs/GaAs multi-quantum well structure 1607, and a p-AlAsselectively oxidized layer 1605.

In this device of Example 16, each n-AlAs selectively oxidized layer1604 is formed at each corresponding one of the joints of the standingwave of oscillating light, starting from the one closest to theresonance region 1611, in the n-Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 1603. There are three n-AlAsselectively oxidized layers 1604 in total. Each of the n-AlAsselectively oxidized layers 1604 is thicker than the p-AlAs selectivelyoxidized layer 1605. The thicknesses of the AlAs selectively oxidizedlayers 1604 and 1605 of two different types are adjusted so that eachside of each non-oxide region 1613 b becomes 5 μm long, and that eachside of the non-oxide region 1613 a becomes 10 μm long. Here, theselective oxidation structures that include the non-oxide regions 1613 bserve as optical mode control structures.

The intra-cavity contact-type surface-emitting laser diode of FIG. 31has two or more (three) oxidized layers in the lower distributed Braggreflector, and employs two or more non-oxide regions 1613 b. With thisstructure, the transverse-mode selecting capacity is increased, andsingle fundamental transverse-mode oscillation can be achieved with highoutputs.

As described above, a long-wave band intra-cavity contact-typesurface-emitting laser diode with an excellent performance can beobtained.

Example 17

FIG. 32 illustrates a surface-emitting laser diode of Example 17 of thepresent invention. The surface-emitting laser diode shown in FIG. 32 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. This device of Example17 has the same structure as the device of Example 16, except that thep-side and n-side electrodes are both provided on the outer surface ofthe device. In the following, this structure will be described indetail.

The device of FIG. 32 has the same layer structure as the device ofExample 16, except that the p-side and n-side electrodes are provided onthe surface of the substrate. In this device, a non-dopedAl_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Bragg reflector1703 is employed as the lower distributed Bragg reflector, andselectively oxidized layers 1704 each including a non-oxide region 1713b having a small area are located in the non-dopedAl_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Bragg reflector1703, not in a resonance region 1711. There are two or more (three)selectively oxidized layers 1704. The layer structure of the resonanceregion 1711 is substantially the same as the resonance region of Example12, and therefore explanation of the layer structure is omitted in thisdescription.

The surface-emitting laser diode of FIG. 32 includes a semi-insulatingGaAs substrate 1701, a non-doped GaAs buffer layer 1702, the non-dopedAl_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Bragg reflector1703, the resonance region 1711, and a non-doped Al_(0.8)Ga_(0.2)As/GaAsupper semiconductor distributed Bragg reflector 1708. These layers areformed through crystal growth in this order, with the semi-insulatingGaAs substrate 1701 being at the bottom.

The resonance region 711 is formed by a GaAs resonator spacer layer1706, a GaInNAs/GaAs multi-quantum well structure 1707, and a p-AlAsselectively oxidized layer 1705.

In this device of FIG. 32, each non-doped AlAs selectively oxidizedlayer 1704 is formed at each corresponding one of the joints of thestanding wave of oscillating light, starting from the one closest to theresonance region 1711, in the non-doped Al_(0.8)Ga_(0.2)As/GaAs lowersemiconductor distributed Bragg reflector 1703. There are threenon-doped AlAs selectively oxidized layers 1704 in total. Each of thenon-doped AlAs selectively oxidized layers 1704 is thicker than thep-AlAs selectively oxidized layer 1705. The thicknesses of the AlAsselectively oxidized layers 1704 and 1705 of two different types areadjusted so that each side of each non-oxide region 1713 b becomes 5 μmlong, and that each side of the non-oxide region 1713 a becomes 10 μmlong.

In the device of FIG. 32, after the crystal growth of the layers, a mesais formed, and selective oxidation is carried out to form a selectiveoxide region 1712 and the non-oxide regions 1713 a and 1713 b. As eachof the non-doped AlAs selectively oxidized layers 1704 is thicker thanthe p-AlAs selectively oxidized layer 1705, the area of each non-oxideregion 1713 b is smaller than the area of the non-oxide region 1713 a.Here, the selective oxidation structures that include the non-oxideregions 1713 b serve as high-order transverse-mode suppressing layers.

The intra-cavity contact-type surface-emitting laser diode of FIG. 32has two or more (three) oxidized layers in the non-dopedAl_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Bragg reflector1703, and employs two or more non-oxide regions 1713 b. With thisstructure, the transverse-mode selecting capacity is further increased,and single fundamental transverse-mode oscillation can be achieved withhigh outputs. Also, the device resistance remains very low, because thenon-oxide regions 1713 b each having a small area is provided outsidethe current passage.

As described above, a long-wave band intra-cavity contact-typesurface-emitting laser diode with an excellent performance can beobtained.

Example 18

FIG. 33 illustrates a surface-emitting laser diode of Example 18 of thepresent invention. The surface-emitting laser diode shown in FIG. 33 isa 1.3 μm band surface-emitting laser diode having a GaInNAs/GaAsmulti-quantum well structure as an active layer. Each of theintra-cavity contact-type surface-emitting laser diodes of the foregoingexample's has the n-conductivity at the substrate side in the resonanceregion. However, this device of Example 18 has the p-conductivity at thesubstrate side in the resonance region. In the following, this structurewill be described in detail.

The device of FIG. 33 includes a semi-insulating GaAs substrate 1801, anon-doped GaAs buffer layer 1802, a 36-period non-doped AlAs/GaAs lowersemiconductor distributed Bragg reflector 1803 having each combinationof AlAs/GaAs as one period, a resonance region 1811, and a 20-periodnon-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Braggreflector 1808 having each combination of Al_(0.8)Ga_(0.2)As/GaAs as oneperiod. These layers are formed through crystal growth in this order,with the semi-insulating GaAs substrate 1801 being at the bottom.

FIG. 34 illustrates the region surrounding the resonance region 1811 ofthe surface-emitting laser diode of FIG. 33 in greater detail. Morespecifically, FIG. 34 shows one period of the non-doped AlAs/GaAs lowersemiconductor distributed Bragg reflector 1803 formed by a non-dopedAlAs lower semiconductor distributed Bragg reflector low refractionlayer 1809 a and a non-doped GaAs lower semiconductor distributed Braggreflector high refraction layer 1809 b, one period of the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector1808 formed by a non-doped Al_(0.8)Ga_(0.2)As upper semiconductordistributed Bragg reflector low refraction layer 1810 a and a non-dopedGaAs upper semiconductor distributed Bragg reflector high refractionlayer 1810 b, and the resonance region 1811 interposed between the oneperiod of the non-doped AlAs/GaAs lower semiconductor distributed Braggreflector 1803 and the one period of the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector1808.

After the non-doped AlAs/GaAs lower semiconductor distributed Braggreflector 1803 is formed through crystal growth, further crystal growthis carried out to form the resonance region 1811 that includes a p-GaAscontact/resonator spacer layer 1806 a, a p-GaAs resonator spacer layer1806 b, a p-AlAs selectively oxidized layer 1805, a p-GaAs resonatorspacer layer 1806 c, a non-doped GaAs resonator spacer layer 1806 d, aGaInNAs/GaAs multi-quantum well structure 1807, a non-doped GaAsresonator spacer layer 1806 e, an n-GaAs resonator spacer layer 1806 f,an n-AlAs selectively oxidized layer 1804, an n-GaAs resonator spacerlayer 1806 g, an n-GaAs contact/resonator spacer layer 1806 h, andnon-doped GaAs resonator spacer layer 1806 i.

In the device of FIG. 33, after the crystal growth of the layers, adouble mesa is formed, and selective oxidation is performed to form aselective oxide region 1812 and non-oxide regions 1813 a and 1813 b.

In the selective oxidizing process for the device of FIG. 33, the n-AlAsselectively oxidized layer 1804 is made thicker than the p-AlAsselectively oxidized layer 1805, so that the area of the non-oxidized(conductive) region 1813 a that is to serve as the hole passage becomeslarger than the area of the non-oxidized (conductive) region 1813 b thatis to serve as the electron passage. More specifically, each side of thenon-oxidized (conductive) region 1813 b that is to serve as the electronpassage is 3 μm long, while each side of the non-oxidized (conductive)region 1813 a that is to serve as the hole passage is 10 μm long. Here,the selective oxidation structure including the non-oxide region 1813 bserves as an optical mode control structure.

The device of FIG. 33 also has a low resistance and high outputs, whilemaintaining single fundamental transverse-mode oscillation.

It is possible for the other devices of the foregoing examples to employthis structure having the p-type conductivity on the substrate side ofthe active layer. This structure having the p-type conductivity on thesubstrate side of the active layer can also be applied to devices otherthan the devices of the foregoing examples.

Although a MOCVD technique is used for crystal growth in each of theforegoing examples, it is also possible to use other crystal growthtechniques such as a molecular beam epitaxy (MBE) technique. Also, ap-type substrate can be employed, instead of an n-type substrate or asemi-insulating substrate. The oscillation wavelength band may be 1.5μm, for example, other than the above mentioned wavelength bands of 670nm, 0.98 μm, 1.3 μm, and 0.85 μm. Also, the semiconductor materials thatconstitute the devices of the foregoing examples may be replaced withother materials, depending on the oscillation wavelength. The devicestructure of each of the foregoing examples may be modified. Thematerials for the distributed Bragg reflectors may also be optimallychanged, depending on the oscillation wavelength. Thus, a device that isoptimally suitable for the oscillation wavelength can be formed inaccordance with any one of the foregoing examples.

The materials that form distributed Braff reflectors such as dielectricreflectors can be replaced with other materials. Also, the lengths andstructures of the resonators can be changed. To reduce the deviceresistance, it is effective to employ a heterospike buffer layer on theheterointerface of Al(Ga)As/GaAs or the like, as a heterospike bufferlayer has such a composition. A heterospike buffer layer may be providedon the interface with a selectively oxidized layer or the like. Examplesof a heterospike buffer layer include a single layer that has thecompositions of the two layers that form a heterointerface, amulti-layer structure containing different compositions, and a layerhaving a composition continually changed.

Example 19

FIG. 35 illustrates a surface-emitting laser diode array of Example 19of the present invention. More specifically, FIG. 35 is a top view of amonolithic laser diode array that two-dimensionally integrates 4×4surface-emitting laser diodes of the present invention. In the exampleshown in FIG. 35, wiring is provided to each upper electrode so as todrive each device independently. The surface-emitting laser diode arrayof FIG. 35 is fabricated in the same manner and by the same method as ineach of the foregoing examples.

Each of the devices that constitute the surface-emitting laser diode ofFIG. 35 has a high-order transverse-mode suppressing layer that isformed by a selective oxidation structure having a small non-oxideregion in the electron passage or in a non-conductive region. Thishigh-order transverse-mode suppressing layer suppresses high-ordertransverse-mode oscillation, without an increase of the deviceresistance. Each device also has a selective oxidation structure havinga large non-oxide region in a p-type distributed Bragg reflector.

This selective oxidation structure restricts the hole-restricting regionto the center of the mesa, without a rapid increase of the deviceresistance.

Accordingly, each device has a low resistance and a wider oscillationregion. With these devices, single fundamental transverse-modeoscillation can be achieved with high outputs, while suppressing heatgeneration. Thus, a surface-emitting laser diode array that performshigh-output operations in the single transverse mode can be obtained.

Example 20

FIGS. 36 and 37 illustrate a multi-wave surface-emitting laser diodearray of Example 20 of the present invention. FIG. 36 shows themulti-wave surface-emitting laser diode array that is formed by 2×3 1.55μm band surface-emitting laser diodes each having a GaInNAsSb/GaAsmulti-quantum well structure as an active layer. FIG. 37 illustrates thestructures of two neighboring devices A and B in a region A in themulti-wave surface-emitting laser diode array of FIG. 36.

Each of the 1.55 μm band surface-emitting laser diodes of the multi-wavesurface-emitting laser diode array of Example 20 has the same structureas the surface-emitting laser diode of Example 11, as can be seen fromFIG. 37. However, the thicknesses of the layers that form eachsurface-emitting laser diode are adjusted so as to conform to theoscillation wavelength band of 1.55 μm. As can be seen from FIG. 37,each device of the multi-wave surface-emitting laser diode array ofExample 20 has an intra-cavity contact structure in which the electrodefor confining carries is provided on a semiconductor layer in thesurface-emitting laser diode, and has a selective oxidation structurefor transverse-mode oscillation control in a region that does not meetthe carrier conduction region.

This multi-wave surface-emitting laser diode array of Example 20 alsohas a p-side electrode on the upper surface of each surface-emittinglaser diode, so that each surface-emitting laser diode can be drivenindependently. Further, an n-side common electrode is provided on thebottom surface of the substrate.

In this multi-wave surface-emitting laser diode array of Example 20, themesa sizes of the surface-emitting laser diodes differ from one another.In FIG. 36, the upper mesa sizes gradually become greater toward theleft. Between the two neighboring devices A and B shown in FIG. 37, forinstance, the mesa size of the device A is greater than the mesa size ofthe device B.

In the following, the structure of this multi-wave surface-emittinglaser diode array of Example 20 will be described in greater detail.Each surface-emitting laser diode shown in FIG. 37 is formed by n-GaAssubstrate 1901, an n-GaAs buffer layer 1902, ann-Al_(0.8)Ga_(0.2)As/GaAs lower semiconductor distributed Braggreflector 1903, a resonance region 1911, and a non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector1908. These layers are formed in this order through crystal growth, withthe substrate 1901 being at the bottom.

Here, the non-doped Al_(0.8)Ga_(0.2)As/GaAs upper semiconductordistributed Bragg reflector 1908 has a non-doped AlAs selectivelyoxidized layer 1904 formed therein.

Like the resonance region of Example 6, the resonance region 1911 isformed by a GaAs resonator spacer layer 1906, a GaInNAsSb/GaAsmulti-quantum well structure 1907, and a p-AlAs selectively oxidizedlayer 1905. The p-AlAs selectively oxidized layer 1905 is thinner thanthe non-doped AlAs selectively oxidized layer 1904. The layer structureof the resonance region 1911 is the same as the layer structure of theresonance region of Example 6.

Etching is then performed twice to form a double square mesa for eachdevice by the same known photoengraving technique and the same knownetching technique as the techniques utilized in each of the foregoingexamples. Here, the upper mesa sizes are varied in the surface-emittinglaser diode array. In FIG. 37, the upper mesa size of the device A isgreater than the upper mesa size of the device B, as already mentioned.After that, selective oxidation is performed on the two selectivelyoxidized layers 1905 and 1904, to thereby form a selective oxide region1912 and non-oxide regions 1913 a and 1913 b/1913 c.

Being relatively thicker than the non-doped AlAs selectively oxidizedlayer 1904, the p-AlAs selectively oxidized layer 1905 has a higheroxidation rate than the non-doped selectively oxidized layer 1904. Thearea of the non-oxide region 1913 a is larger than the area of thenon-oxide region 1013 b/1913 c. The oxidation rate of the non-doped AlAsselectively oxidized layer 1904 of the device A is the same as theoxidation rate of the non-doped AlAs selectively oxidized layer 1904 ofthe device B. However, as the upper mesa size of the device A is greaterthan the upper mesa size of the device B, the area of the non-oxideregion 1913 b is larger than the area of the non-oxide region 1913 c.Here, each selective oxidation structure that includes the non-oxideregion 1913 b/1913 c serves as an optical mode control structure.

In the multi-wave surface-emitting laser diode array of FIG. 36, theupper mesa sizes of the surface-emitting laser diodes that constitutethe array are different from one another. Likewise, the areas of thenon-oxide regions formed in the non-doped AlAs selectively oxidizedlayers 1904 are different from one another, as already mentioned.

A SiO₂ insulating layer 1914 is then formed for each of thesurface-emitting laser diodes, and a p-side electrode 1915 is formed bya vapor deposition technique and a lift-off technique for each of thesurface-emitting laser diodes. An n-side electrode 1916 is thendeposited on the bottom surface of the substrate, and Ohmic conductionis carried out through annealing, to thereby complete the multi-wavesurface-emitting laser diode array of FIGS. 36 and 37.

In the surface-emitting laser diode array of FIG. 36, the areas of thenon-oxide regions of the optical mode control structures of thesurface-emitting laser diodes are different from one another, andaccordingly, the oscillation wavelengths of the surface-emitting laserdiodes are different from one another. A surface-emitting laser diodehaving a smaller non-oxide region in the optical mode control structurecan attain greater oscillation in a short-wave band area. The wavelengthintervals among the surface-emitting laser diodes that constitute themulti-wave surface-emitting laser diode array of Example 20 are 1 nm,and attain oscillation wavelengths of 1546 nm to 1553 nm.

In each of the surface-emitting laser diodes of FIG. 36, currentconfining is not performed via the upper semiconductor distributed Braggreflector, which is a non-doped type. As a p-type distributed Braggreflector that has high light absorptivity is not employed in each ofthe surface-emitting laser diodes of FIG. 36, the surface-emitting laserdiode array has only a small loss. Also, the oscillation thresholdcurrent is low, and the slope efficiency is high. The surface-emittinglaser diode array can also have high outputs.

Since the optical mode control structure is provided in the non-dopedAl_(0.8)Ga_(0.2)As/GaAs upper semiconductor distributed Bragg reflector1908 in each surface-emitting laser diode, the non-oxide region 1913b/1913 c does not affect the device resistance. Accordingly, each of thesurface-emitting laser diode has a very low resistance, and generateslittle heat. The surface-emitting laser diodes of FIG. 36 can thusperform high-output operations. Also, the current restriction in each ofthe surface-emitting laser diodes of FIG. 36 is performed by theselective oxidation structure formed through selective oxidationperformed on the p-AlAs selectively oxidized layer 1905 provided in theresonance region. By doing so, variations of the oscillation thresholdcurrent and operation voltage among the surface-emitting laser diodescan be made very small within the array. Thus, a multi-wavesurface-emitting laser diode array of uniform characteristics can beobtained. This multi-wave surface-emitting laser diode array of Example20 can have high outputs, while maintaining single fundamentaltransverse-mode oscillation.

Although a multi-wave surface-emitting laser diode array that includes2×3 surface-emitting laser diodes has been described, it is possible toemploy a different array structure (having a different number ofdevices, or a different layout of devices).

Example 21

FIG. 38 illustrates a surface-emitting laser diode of Example 21 of thepresent invention. The surface-emitting laser diode shown in FIG. 38 isa 1.3 μm band surface-emitting laser diode that has a GaInNAs/GaAsmulti-quantum well structure as an active layer, and is formed on ap-type semiconductor substrate, which is the same as in Example 5. Thestructure of this surface-emitting laser diode of Example 21 is the sameas the structure of the device of Example 5, except for the oscillationwavelength, the materials for the active layer, and the composition ofsemiconductor materials that form the distributed Bragg reflectors. Inshort, the structure of this example is fundamentalally the same as thestructure described in Example 5. However, the thicknesses of the layersare adjusted based on the oscillation wavelength. Also, the compositionof the semiconductor materials that form the semiconductor distributedBragg reflectors is made transparent with respect to the oscillationwavelength.

As shown in FIG. 38, the width of the mesa of the surface-emitting laserdiode of Example 21 is smaller at the top and is greater at the bottom(a tapered shape). In the following, this structure will be described indetail.

The surface-emitting laser diode of FIG. 38 includes: a p-GaAs substrate2001; a p-GaAs buffer layer 2002; a 36-period p-Al_(0.9)Ga_(0.1)As/GaAslower semiconductor distributed Bragg reflector 2003 having eachcombination of Al_(0.9)Ga_(0.1)As/GaAs as one period; a resonance region2011 that is formed by a GaAs resonator spacer 2005 and a GaInNAs/GaAsmulti-quantum well active layer 2006; and a 26-periodn-Al_(0.9)Ga_(0.1)As/GaAs upper semiconductor distributed Braggreflector 2008. These layers are formed in this order through crystalgrowth, with the substrate 2001 being at the bottom.

The p-Al_(0.9)Ga_(0.1)As/GaAs lower semiconductor distributed Braggreflector 2003 and the n-Al_(0.9)Ga_(0.1)As/GaAs upper semiconductordistributed Bragg reflector 2008 include a p-AlAs selectively oxidizedlayer 2004 and an n-AlAs selectively oxidized layer 2009, respectively.The AlAs selectively oxidized layers 2004 and 2009 have the samethickness (20 nm). The structure of the resonance region 2011 is thesame as the resonance region of Example 5.

In the device of FIG. 38, after the crystal growth of the layers, aresist mask is formed by a known photoengraving technique. The squaremesa having the tapered shape shown in FIG. 38 is then formed. To formsuch a tapered shape through etching, a known area gradation mask isemployed as a photomask in forming the resist mask, or the dry etchingconditions are optimally adjusted. In this device of Example 21, theconvex resist mask is formed with an area gradation mask, followed byetching. A wet etching technique may also be utilized to form thetapered mesa. In that case, the conditions such as the mask shape, theetching liquid, the etching technique, should be selected suitably forthe wet etching.

After the formation of the tapered mesa, selective oxidation isperformed on the p-AlAs partially oxidize layer 2004 and the n-AlAsselectively oxidized layer 2009, to thereby form a selective oxideregion 2012 and non-oxidized (conductive) regions 2013 a and 2013 b thathave different areas. Here, the selective oxidation structure thatincludes the non-oxide region 2013 b serves as a high-ordertransverse-mode suppressing layer, and the selective oxidation structurethat includes the non-oxide region 2013 a serves as a hole restrictinglayer.

As the surface-emitting laser diode of Example 21 has the tapered mesa,the part of the mesa that includes the p-AlAs selectively oxidized layer2004 forming the hole confioning structure through the selectiveoxidation is greater in size than the part of the mesa that includes then-AlAs selectively oxidized layer 2009 forming the high-ordertransverse-mode suppressing layer through the selective oxidation.Accordingly, after the oxidation of the same lengths in the selectivelyoxidized layers 2004 and 2009 at the same oxidation rate, the p-AlAsselectively oxidized layer 2004 that is located in an antinode of themesa has the larger non-oxide region 2013 b by virtue of the differencesin mesa size. Thus, the area of the non-oxidized (conductive) region2013 b in the electron passage is smaller than the area of thenon-oxidized (conductive) region 2013 a in the hole passage.

After the selective oxidation, an insulating region including a SiO₂insulating 2014 and insulating resin 2015 is formed. A p-side electrode2016 and an n-side electrode 2017 are then formed to complete thesurface-emitting laser diode of FIG. 38.

The surface-emitting laser diode of FIG. 38 can have high outputs, whilemaintaining single fundamental transverse-mode oscillation.

As described above, instead of two or more mesas of different sizes thathave vertical etching sides, a tapered mesa in which the mesa size istapered can be employed in the present invention.

Example 22

FIG. 39 illustrates a surface-emitting laser diode of Example 22 of thepresent invention. The surface-emitting laser diode shown in FIG. 39 isa 0.85 μm band surface-emitting laser diode having aGaAs/Al_(0.15)Ga_(0.85)As multi-quantum well structure as an activelayer. This surface-emitting laser diode of FIG. 39 has an intra-cavitycontact structure in which the electrode for confining carriers isprovided on a semiconductor layer in the device. Also, this device ofExample 22 has the selective oxidation structure for transverse-modeoscillation control in a region that does not meet the carrierconduction region.

The structure of the surface-emitting laser diode of FIG. 39 is the sameas the device of Example 11, except for the oscillation wavelength, thematerials for the active layer, the resonator spacer layers, and thecomposition of semiconductor materials that form distributed Braggreflectors. In short, the layer structure of this example isfundamentalally the same as the layer structure described in Example 11.However, the thickness of each layer is adjusted based on theoscillation wavelength. Also, the composition of the semiconductormaterials that form the semiconductor distributed Bragg reflectors aremade transparent with respect to the oscillation wavelength. Morespecifically, the GaAs resonator spacer of Example 11 is replaced by anAl_(0.15)Ga_(0.85)As resonator spacer layer, and the upper and lowerAl_(0.8)Ga_(0.2)As/GaAs semiconductor distributed Bragg reflectors ofExample 11 are replaced by Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)Assemiconductor distributed Bragg reflectors. The thickness of each layeris adjusted so as to satisfy the resonance conditions with respect tothe oscillation wavelength.

The surface-emitting laser diode of FIG. 39 also includes two selectiveoxidation structures having different non-oxide regions that are formedthrough selective oxidation performed on selectively oxidized layerscontained in mesas of different sizes, respectively. In the following,this structure will be described in detail.

The device of FIG. 39 includes an n-GaAs substrate 2101, an n-GaAsbuffer layer 2102, an n Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As lowersemiconductor distributed Bragg reflector 2103, a resonance region 2111,and a non-doped Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As uppersemiconductor distributed Bragg reflector 2108. These layers are formedin this order through crystal growth, with the substrate 2101 being atthe bottom.

The resonance region 2111 is formed by an Al_(0.15)Ga_(0.85)As resonatorspacer region 2106, a GaAs/Al_(0.15)Ga_(0.85)As multi-quantum wellstructure 2107, and a p-AlAs selectively oxidized layer 2105. Thenon-doped Al_(0.9)Ga_(0.1)As/Al_(0.15)Ga_(0.85)As upper semiconductordistributed Bragg reflector 2108 includes a non-doped AlAs selectivelyoxidized layer 2104. Here, the p-AlAs selectively oxidized layer 2105and the non-doped AlAs selectively oxidized layer 2104 have the samethickness (20 nm).

In the device of FIG. 39, after the crystal growth of the layers, twosquare mesas of different sizes are formed by a known photoengravingtechnique and a known etching technique. In this example, the size (thelength of each side) of the upper mesa is 10 μm, and the size (thelength of each side) of the lower mesa is 18 μm. As shown in FIG. 39,the upper mesa includes the non-doped AlAs selectively oxidized layer2104, and the lower mesa includes the p-AlAs selectively oxidized layer2105.

Selective oxidation is then performed on the non-doped AlAs selectivelyoxidized layer 2104 and the p-AlAs selectively oxidized layer 2105, tothereby form a selective oxide region 2112 and non-oxidized (conductive)regions 2113 a and 2113 b that have different areas. As the sizes of themesas that include the non-doped AlAs selectively oxidized layer 2104and the p-AlAs selectively oxidized layer 2105 differ from each other,the area of the non-oxide region 2113 a of the p-AlAs selectivelyoxidized layer 2105 included in the lower mesa that is the greater insize becomes larger, after the oxidation of the same lengths in the twoselectively oxidized layers 2104 and 2105 at the same oxidation rates.

In each of the selectively oxidized layers 2104 and 2105, the oxidationis performed on the peripheral area of 3.5 μm in width. As a result,each side of the non-oxide region 2113 a is 11 μm long, and each side ofthe non-oxide region 2113 b is 3 μm long.

Here, the selective oxidation structure that includes the smallernon-oxide region 2113 b serves as an optical mode control structure.Also, the selective oxidation structure that includes the largernon-oxide region 2113 a serves as a hole restricting structure.

A SiO₂ insulating layer 2114, a p-side electrode 2115, and an n-sideelectrode 2116 are then formed, to thereby complete the surface-emittinglaser diode of FIG. 39.

The surface-emitting laser diode of FIG. 39 does hot guide current viathe upper semiconductor distributed Bragg reflector, which is anon-doped type. As a p-type distributed Bragg reflector having a highlight absorptivity is not employed in the surface-emitting laser diodeof FIG. 39, the light loss is very low. Accordingly, the oscillationthreshold current is small, and the slope efficiency is high.Furthermore, as the non-oxide region 2113 b provided in the non-dopedAl_(0.9)Ga_(0.1)As/GaAs upper semiconductor distributed Bragg reflector2108 does not affect the resistance, the device resistance can remainvery low.

The surface-emitting laser diode of FIG. 39 can perform high-outputoperations, being able to have high outputs, while maintaining singlefundamental transverse-mode oscillation.

In this example, the selective oxidation structures having differentnon-oxide regions are formed by a one-time oxidation process, utilizingthe differences in thickness and Al composition between the twoselectively oxidized layers, and the size difference between the upperand lower mesas. However, it is also possible to oxidize the partialoxidized layers separately, or to perform selective oxidation twice ormore on the same selectively oxidized layer. For example, the order ofthe mesa forming etching process and the oxidation process can bechanged, or the etching depth in the mesa formation can be optimallychanged. Also, an oxidation protection film or the like may be formed onthe side surfaces of the selectively oxidized layers, so that theselectively oxidized layers can be oxidized separately.

Example 23

FIG. 40 illustrates an electrophotographic system of Example 23 of thepresent invention. The electrophotographic system of FIG. 40 includes aphotosensitive drum, an optical scan system (a scan converging opticalsystem), a WRITE light source, and a synchronous control circuit (asynchronization controller). In this electrophotographic system, asurface-emitting laser diode or a surface-emitting laser diode array ofthe present invention is employed as the WRITE light source.

The electrophotographic system of FIG. 40 is controlled by thesynchronous control circuit, and beams from the WRITE light source aregathered onto the photosensitive drum by the scan converging opticalsystem that includes a polygon mirror and a lens converging system. Alatent image is thus formed on the photosensitive drum. Conventionally,a surface-emitting laser diode often fails to perform a high-outputoperation, due to adverse influence of heat generation. However, asurface-emitting laser diode of the present invention readily performshigh-output operations, and accordingly, can be employed as the WRITElight source of an electrophotographic system. As the oscillation modeis the single fundamental transverse mode in a surface-emitting laserdiode of the present invention, a far visual field image is asingle-peaked type. As the beam condensing is also easy, ahigh-definition full-color image can be obtained.

A red surface-emitting laser diode having an AlGaInP material as anactive layer material can have an oscillation wavelength of 650 nm,which is shorter than an oscillation wavelength with an AlGaAs material.Therefore, more freedom can be allowed for the designing in the opticalsystem. Accordingly, such a red surface-emitting laser diode is suitablefor the WRITE light source of a high-definition full-colorelectrophotographic system. Such a red surface-emitting laser diode canemploy an AlGaInP material as an active layer, and AlGaAs and AlGaInPmaterials as distributed Bragg reflectors. Since these materials can begrown through crystal growth in a lattice arrangement on a GaAssubstrate, an AlAs material or the like can be used as selectivelyoxidized layers. However, as an AlGaInP material is easily affected by atemperature change, there will be problems, such as output saturationand oscillation stop, due to a temperature rise caused by heatgeneration of the device. To avoid these problems, the redsurface-emitting laser diode of the present invention employs an opticalmode control structure that is formed by a selective oxidation structureincluding a small non-oxide region in the electron passage or in anon-conductive region. With this structure, high-order transverse-modeoscillation can be suppressed, without an increase of the deviceresistance. Furthermore, it is unnecessary to perform transverse-modeoscillation control with a conventional single oxidation confinementstructure provided a p-type Bragg reflector or the like in the holepassage. Accordingly, it is unnecessary to form a very small currentrestriction structure, so that the device resistance can be made low. Asurface-emitting laser diode of the present invention has less heatgeneration, and can perform high-output operation with higherefficiency, while maintaining single fundamental transverse-modeoscillation. In view of these facts, a surface-emitting laser diode or asurface-emitting laser diode array of the present invention is suitablefor the WRITE light source of an electrophotographic system.

Particularly, with the surface-emitting laser diode array of Example 19,a multi-beam write system with a higher write speed can be realized.Thus, a high-speed, high-definition full-color electrophotographicsystem can be obtained.

Example 24

FIG. 41 schematically illustrates a surface-emitting laser diode moduleof Example 24 of the present invention. The laser diode array module ofFIG. 41 includes a one-dimensional monolithic surface-emitting laserdiode array, a microlens array, and a fiber array, all of which aremounted on a silicon substrate.

In this module, the surface-emitting laser diode array is located on theopposite side from fibers, and is connected, via the microlens array, toquartz single-mode fibers mounted in V-shaped grooves formed in thesilicon substrate. The surface-emitting laser diode array has anoscillation wavelength band of 1.3 μm. With the quartz single-modefibers, high-speed transmission can be performed.

Since the surface-emitting laser diode module of Example 24 employs asurface-emitting laser diode array of the present invention, stablefundamental transverse-mode oscillation can be maintained even whenthere is a change in the drive conditions such as the surroundingtemperature. Also, the connecting rate with the fibers rarely changes.Thus, a highly reliable laser diode module can be obtained.

Example 25

FIG. 42 illustrates an optical interconnection system of Example 25 ofthe present invention. The interconnection system of FIG. 42 has anapparatus 1 and an apparatus 2 that are connected to each other with anoptical fiber array. The apparatus 1, which is a transmission apparatus,includes a one-dimensional laser diode array module formed bysurface-emitting laser diodes or a surface-emitting laser diode array ofthe present invention, and a drive circuit for the module. The apparatus2, which is a reception apparatus, includes a photodiode array moduleand a signal detecting circuit.

As the optical interconnection system of Example 25 employs asurface-emitting laser diode array of the present invention, stablefundamental transverse-mode oscillation can be maintained even whenthere is a change in the drive conditions such as the surroundingtemperature. Also, the connecting rate with the fibers rarely changes.Thus, a highly reliable interconnection system can be obtained.

Although a parallel interconnection system has been described as Example25, it is also possible to obtain a serial transmission system thatincludes a single device. Furthermore, an interconnection structure ofthe present invention can be formed between boards, chips, or inside achip.

Example 26

FIG. 43 illustrates an optical communication system of Example 26 of thepresent invention. The optical communication system of FIG. 43 is anoptical LAN system that includes surface-emitting laser diodes orsurface-emitting laser diode array devices of the present invention.More specifically, surface-emitting laser diodes or surface-emittinglaser diode arrays of the present invention are employed as lightsources for optical transmission between servers and a core switch,between the core switch and switches, and between the switches andterminals.

In this optical communication system, apparatuses are connected withquartz single-mode fibers or multi-mode fibers. As the physical layer ofsuch an optical LAN, Gigabit Ethernet such as 1000BASE-LX can beemployed. As the optical LAN system of FIG. 43 includes surface-emittinglaser diodes of the present invention as light sources, stablefundamental transverse-mode oscillation can be maintained even whenthere is a change in the drive conditions such as the surroundingtemperature. Also, the connecting rate with the fibers rarely changes.Thus, a highly reliable interconnection system can be obtained.

Example 27

FIG. 44 illustrates a wavelength division multiplexing (WDM)communication system of Example 27 of the present invention.

The WDM communication system of FIG. 44 includes light sources formed bymulti-wave surface-emitting laser diode arrays of the present invention,a WDM combiner, quartz multi-mode fibers, a WDM divider, and lightreceivers.

In this system, arrayed waveguide gratings (AWG) may be employed as thedivider and the combiner. Also, surface-emitting laser diode arrays eachhaving a GaInNAsSb material as an active layer and having an oscillationwavelength band of 1.55 μm, which is the same as the surface-emittinglaser diode array of Example 20, can be employed as the multi-wavesurface-emitting laser diode arrays. Here, the wavelength intervalsamong the surface-emitting laser diodes in each surface-emitting laserdiode array are 1 nm. In the WDM communication system of FIG. 44, foursurface-emitting laser diode arrays each including eight devices andhaving different center wavelengths are employed to thereby form a32-channel system. Signals transmitted from the surface-emitting laserdiodes of each surface-emitting laser diode array are combined by thecombiner, and are transmitted through one multi-mode fiber. Based on thewavelengths, the divider distributes the transmitted signals to thelight receivers, which convert the transmitted signals to electricsignals.

The multi-wave surface-emitting laser diode arrays that serve as thelight sources in this optical communication system of Example 27 canhave high outputs, while maintaining fundamental single transverse-modeoscillation, because each surface-emitting laser diode in the arrays hasa very low resistance. Accordingly, high-speed modulation can beperformed, and the characteristics of the surface-emitting laser diodes,such as the oscillation threshold current, are almost uniform in eacharray. With this structure, it is not necessary to employ a complicateddrive circuit for driving each array. Thus, a highly reliable WDMcommunication system can be obtained at low costs.

Although the WDM communication system of 1.55 μm band has been describedas Example 27, other wavelength bands such as a 1.3 μm band can be used.Depending on the wavelength band, the materials and compositions of thedevices that form the multi-wave surface-emitting laser diode arrays canbe optimally selected. It is also possible to change the number ofchannels and the wavelength intervals, if necessary. Instead of thequartz multi-mode fibers, quartz single-mode fibers or POFs (PlasticOptical Fibers) can be employed as optical fibers, so that optimumfibers can be selected for the wavelength band that is being used.

It should be noted that the present invention is not limited to theembodiments specifically disclosed above, but other variations andmodifications may be made without departing from the scope of thepresent invention.

1. A surface-emitting laser diode device that oscillates in the direction perpendicular to a substrate, comprising: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole confinign structure that is provided in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, the area of the non-oxide region being smaller than the area of the hole restricting structure.
 2. The surface-emitting laser diode device as claimed in claim 1, wherein the hole restricting structure includes a non-oxide region and an oxide region surrounding the non-oxide region, both regions being formed out of a semiconductor layer containing Al as a constituent element.
 3. The surface-emitting laser diode device as claimed in claim 2, wherein the hole restricting structure and the optical mode control structure each includes an oxide region and a non-oxide region that are formed through selective oxidation performed on a part of a semiconductor layer, each region containing Al as a constituent element.
 4. The surface-emitting laser diode device as claimed in claim 1, wherein the optical mode control structure is provided in the electron passage.
 5. The surface-emitting laser diode device as claimed in claim 1, wherein the optical mode control structure is provided in a region that does not meet the electron passage and the hole passage.
 6. The surface-emitting laser diode device as claimed in claim 5, wherein the part of the hole restricting structure that defines the region for confining holes is formed by a p-type semiconductor layer.
 7. The surface-emitting laser diode device as claimed in claim 1, wherein: the part of the hole restricting structure that defines the region for confining holes is formed by a p-type semiconductor layer; and the non-oxide region in the optical mode control structure is formed by a n-type semiconductor layer.
 8. The surface-emitting laser diode device as claimed in claim 1, wherein the first distributed Bragg reflector and the second distributed Bragg reflector are formed by laminated structures of semiconductor layers.
 9. The surface-emitting laser diode device as claimed in claim 1, wherein one of the first distributed Bragg reflector and the second distributed Bragg reflector is formed by a laminated structure of semiconductor layers, while the other one is formed by a laminated structure of semiconductor or dielectric layers.
 10. The surface-emitting laser diode device as claimed in claim 1, wherein: at least one of the first distributed Bragg reflector and the second distributed Bragg reflector is a semiconductor Bragg reflector having a laminated structure of n-type semiconductor layers, and a tunnel junction is interposed between the n-type semiconductor Bragg reflector and the active layer.
 11. The surface-emitting laser diode device as claimed in claim 1, wherein: at least one of the first distributed Bragg reflector and the second distributed Bragg reflector includes a laminated structure of non-doped semiconductor layers; and one of the first electrode and the second electrode is provided on a semiconductor layer interposed between the active layer and the distributed Bragg reflector that includes the laminated structure of the non-doped semiconductor layer.
 12. The surface-emitting laser diode device as claimed in claim 1, wherein the hole restricting structure is provided at a location corresponding to an antinode of the standing wave of oscillating light in the resonator structure.
 13. The surface-emitting laser diode device as claimed in claim 1, wherein a plurality of optical mode control structures each having the same structure as the optical mode control structure are provided in the electron passage.
 14. The surface-emitting laser diode device as claimed in claim 1, wherein a plurality of optical mode control structures each having the same structure as the optical mode control structure are provided in a region that does not meet the electron passage and the hole passage.
 15. The surface-emitting laser diode device as claimed in claim 3, wherein the semiconductor layer that forms the optical mode control structure through selective oxidation and contains Al as a constituent element is thicker than the semiconductor layer that forms the hole restricting structure through selective oxidation and contains Al as a constituent element.
 16. The surface-emitting laser diode device as claimed in claim 3, wherein the Al content of the semiconductor layer that forms the optical mode control structure through selective oxidation and contains Al as a constituent element is greater than the Al content of the semiconductor layer that forms the hole restricting structure through selective oxidation and contains Al as a constituent element.
 17. The surface-emitting laser diode device as claimed in claim 1, wherein the active layer is formed by a III-V semiconductor material that includes at least one III-group element selected from the group of Al, Ga, and In, and at least one V-group element selected from the group of As and P, the active layer having an oscillation wavelength shorter than 1.1 μm.
 18. The surface-emitting laser diode device as claimed in claim 1, wherein the active layer is formed by a III-V semiconductor material that includes at least one III-group element selected from the group of Ga and In, and at least one V-group element selected from the group of As, P, N, and Sb, the active layer having an oscillation wavelength longer than 1.1 μm.
 19. A surface-emitting laser diode array that is monolithically formed on a substrate, each device that is a part of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is provided in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 20. A surface-emitting laser diode array that is monolithically formed on a substrate, each device that is a part of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is provided in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the areas of the non-oxide regions of the optical mode control structures being different from one another among the devices that form the surface-emitting laser diode array, and oscillation wavelengths being also different from one another among the devices.
 21. The surface-emitting laser diode array as claimed in claim 19, wherein each of the devices that form the surface-emitting laser diode array includes a plurality of optical mode control structures each having the same structure as the optical mode control structure.
 22. A surface-emitting laser diode module comprising: an optical fiber; and a surface-emitting laser diode device that is optically connected to the optical fiber, the surface-emitting laser diode device including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 23. A surface-emitting laser diode array module comprising: a plurality of optical fibers; and a surface-emitting laser diode array that is optically connected to each of the optical fibers, the surface-emitting laser diode array being monolithically formed on a substrate, the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 24. An electrophotographic apparatus comprising: a light source; an optical scan system that deflects optical beams emitted from the optical source; and a photosensor on which optical write is performed with the optical beams deflected by the optical scan system, the light source including a surface-emitting laser diode device that includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 25. An electrophotographic apparatus comprising: a light source; an optical scan system that deflects optical beams emitted from the optical source; and a photosensor on which optical write is performed with the optical beams deflected by the optical scan system, the light source including a surface-emitting laser diode array that is monolithically formed on a substrate, each device of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 26. An optical interconnection system comprising: a light source; a light receiving element; and an optical fiber that optically connects the light source and the light receiving element, the light source including a surface-emitting laser diode device that includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 27. An optical interconnection system comprising: a light source; a light receiving element; and an optical fiber that optically connects the light source and the light receiving element, the light source including a surface-emitting laser diode array that is monolithically formed on a substrate, each device of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 28. An optical interconnection system comprising: a light source; a light receiving element; and an optical fiber that optically connects the light source and the light receiving element, the light source including a surface-emitting laser diode array that is monolithically formed on a substrate, each device of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the areas of the non-oxide regions of the optical mode control structures being different from one another among the devices that form the surface-emitting laser diode array, and oscillation wavelengths being also different from one another among the devices.
 29. An optical communication system comprising: a light source unit; a light receiving unit; and an optical fiber that optically connects the light source unit and the light receiving unit, the light source unit including a surface-emitting laser diode device that includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 30. An optical communication system comprising: a light source unit; a light receiving unit; and an optical fiber that optically connects the light source unit and the light receiving unit, the light source unit including a surface-emitting laser diode array that is monolithically formed on a substrate, each device of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure.
 31. An optical communication system comprising: a light source unit; a light receiving unit; and an optical fiber that optically connects the light source unit and the light receiving unit, the light source unit including a surface-emitting laser diode array that is monolithically formed on a substrate, each device of the surface-emitting laser diode array including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and defines a region for confining holes to the active layer; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the areas of the non-oxide regions of the optical mode control structures being different from one another among the devices that form the surface-emitting laser diode array, and oscillation wavelengths being also different from one another among the devices.
 32. A method of fabricating a surface-emitting laser diode device that includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and includes a non-oxide region that defines a region for confining holes to the active layer, and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the method comprising the steps of: forming the hole restricting structure including the oxide region and the non-oxide region by selectively oxidizing a semiconductor layer that contains Al as a constituent element; and forming the optical mode control structure including the oxide region and the non-oxide region by selectively oxidizing a semiconductor layer that contains Al as a constituent element, the step of forming the hole restricting structure and the step of forming the optical mode control structure being performed simultaneously, and the thickness of the semiconductor layer that is to form the hole restricting structure and contains Al as a constituent element being different from the thickness of the semiconductor layer that is to form the optical mode control structure and contains Al as a constituent element.
 33. A method of fabricating a surface-emitting laser diode device that includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and includes a non-oxide region that defines a region for confining holes to the active layer, and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the method comprising the steps of: forming the hole restricting structure including the oxide region and the non-oxide region by selectively oxidizing a semiconductor layer that contains Al as a constituent element; and forming the optical mode control structure including the oxide region and the non-oxide region by selectively oxidizing a semiconductor layer that contains Al as a constituent element, the step of forming the hole restricting structure and the step of forming the optical mode control structure being performed simultaneously, and the Al composition of the semiconductor layer that is to form the hole restricting structure and contains Al as a constituent element being different from the Al composition of the semiconductor layer that is to form the optical mode control structure and contains Al as a constituent element.
 34. A method of fabricating a surface-emitting laser diode device that includes: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and includes a non-oxide region that defines a region for confining holes to the active layer, and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the method comprising the steps of: forming a first mesa that includes a semiconductor layer that contains Al as a constituent element and is to form, through selective oxidation, the hole restricting structure including the oxide region and the non-oxide region; forming a second mesa that includes a semiconductor layer that contains Al as a constituent element and is to form, through selective oxidation, the optical mode control structure including the oxide region and the non-oxide region; forming the hole restricting structure including the oxide region and the non-oxide region by selectively oxidizing the semiconductor layer that contains Al as a constituent element; and forming the optical mode control structure including the oxide region and the non-oxide region by selectively oxidizing the semiconductor layer that contains Al as a constituent element, the step of forming the hole restricting structure and the step of forming the optical mode control structure being performed simultaneously, and the size of the first mesa being different from the size of the second mesa.
 35. A method of fabricating a surface-emitting laser diode array that is formed with devices each including: an active layer; a resonator structure including a first distributed Bragg reflector and a second distributed Bragg reflector that face each other and sandwich the active layer; a hole passage that extends from a first electrode to the active layer; an electron passage that extends from a second electrode to the active layer; a hole restricting structure that is located in the hole passage and includes a non-oxide region that defines a region for confining holes to the active layer, and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element; and an optical mode control structure that includes a non-oxide region provided in the resonator structure and an oxide region surrounding the non-oxide region, each region containing Al as a constituent element, and the area of the non-oxide region being smaller than the area of the hole restricting structure, the areas of the non-oxide regions of the optical mode control structures being different from one another among the devices that form the surface-emitting laser diode array, and oscillation wavelengths being also different from one another among the devices, the method comprising the steps of: forming a first mesa that includes a semiconductor layer that contains Al as a constituent element and is to form, through selective oxidation, the hole restricting structure including the oxide region and the non-oxide region; forming a second mesa that includes a semiconductor layer that contains Al as a constituent element and is to form, through selective oxidation, the optical mode control structure including the oxide region and the non-oxide region, forming the hole restricting structure including the oxide region and the non-oxide region by selectively oxidizing the semiconductor layer that contains Al as a constituent element; and forming the optical mode control structure including the oxide region and the non-oxide region by selectively oxidizing the semiconductor layer that contains Al as a constituent element, the step of forming the hole restricting structure and the step of forming the optical mode control structure being performed simultaneously, and the sizes of the second mesas being different from one another among the devices that have different wavelengths. 